@tbbear great!
Thanks!
Peter

@Mykle1 thanks.
I did something like that.
This part is missing in the nl.json:

"OVERCAST": "Overcast",
"CLOUDY": "Cloudy",
"RAIN": "Rain",
"CLEAR": "Clear",
"PARTLY_CLOUDY": "Partly Cloudy",

So, I copied this from the en.json, pasted it in the nl.json and translated the right side, like this:

"OVERCAST": "Grotendeels bewolkt",
"CLOUDY": "Bewolkt",
"RAIN": "Regen",
"CLEAR": "Helder",
"PARTLY_CLOUDY": "Gedeeltelijk bewolkt",

After restarting MM it shows: Overcast …
Strange about this: in the older version of NOAA the same part is missing in nl.json, but the translation is ok.
So I presume the translation is somewhere else …
Peter

After every update of MMM-NOAA the current weather is back in english again.
Translation of the current weather is not in the Dutch translation file.
Any idea how to fix this definitely?
Peter

@cruunnerr OK, I will follow your advice.
And what to do when I find the module that is causing the ploblem?
Delete it and install it again?
I love all the modules that I use now, so it would be bad not to have them.
Peter

@cruunnerr , shame on me, you are right!
This is my error log:

/home/pi/.pm2/logs/MagicMirror-error-0.log last 15 lines:
0|MagicMir | npm ERR! 
0|MagicMir | npm ERR! Failed at the magicmirror@2.2.2 start script 'sh run-start.sh'.
0|MagicMir | npm ERR! Make sure you have the latest version of node.js and npm installed.
0|MagicMir | npm ERR! If you do, this is most likely a problem with the magicmirror package,
0|MagicMir | npm ERR! not with npm itself.
0|MagicMir | npm ERR! Tell the author that this fails on your system:
0|MagicMir | npm ERR!     sh run-start.sh
0|MagicMir | npm ERR! You can get information on how to open an issue for this project with:
0|MagicMir | npm ERR!     npm bugs magicmirror
0|MagicMir | npm ERR! Or if that isn't available, you can get their info via:
0|MagicMir | npm ERR!     npm owner ls magicmirror
0|MagicMir | npm ERR! There is likely additional logging output above.
0|MagicMir | 
0|MagicMir | npm ERR! Please include the following file with any support request:
0|MagicMir | npm ERR!     /home/pi/MagicMirror/npm-debug.log

Peter

Unfortunately the problem is not solved.
Maybe somebody can have a look at my config.js?

/* Magic Mirror Config Sample
 *
 * By Michael Teeuw http://michaelteeuw.nl
 * MIT Licensed.
 *
 * For more information how you can configurate this file
 * See https://github.com/MichMich/MagicMirror#configuration
 *
 */

var config = {
	address: "localhost", // Address to listen on, can be:
	                      // - "localhost", "127.0.0.1", "::1" to listen on loopback interface
	                      // - another specific IPv4/6 to listen on a specific interface
	                      // - "", "0.0.0.0", "::" to listen on any interface
	                      // Default, when address config is left out, is "localhost"
	port: 8080,
	ipWhitelist: ["127.0.0.1", "::ffff:127.0.0.1", "::1"], // Set [] to allow all IP addresses
	                                                       // or add a specific IPv4 of 192.168.1.5 :
	                                                       // ["127.0.0.1", "::ffff:127.0.0.1", "::1", "::ffff:192.168.1.5"],
	                                                       // or IPv4 range of 192.168.3.0 --> 192.168.3.15 use CIDR format :
	                                                       // ["127.0.0.1", "::ffff:127.0.0.1", "::1", "::ffff:192.168.3.0/28"],

	language: "nl",
	timeFormat: 24,
	units: "metric",


	modules: [
		
		{
			module: 'MMM-WatchDog',
			config: {
			// See 'Configuration options' for more information.
		}
	},
		{
			module: 'mmm-systemtemperature',
			position: 'top_center',	// This can be any of the regions.
			classes: 'xsmall dimmed', // Add your own styling. Optional.
			config: {
			// See 'Configuration options' for more information.
		}
	},
		{
			module: 'mmm-wu-moonphase',
			header: '',   // optionally you can add a header to this block
			position: 'top_center',  // this can be any of the regions.   
			config: {
			// See 'Configuration options' for more information.
			apikey: 'xxxxxxxxxxxx',
			country: 'Nederland',
			city: 'Apeldoorn',
			apiLang: 'NL',
			
		}
		},		 		
		{
			module: "clock",
			position: "top_left"
		},
		{
				module: 'calendar_monthly',
				position: 'top_left',
				config: {
						// The config property is optional
						// Without a config, a default month view is shown
						// Please see the 'Configuration Options' section for more information
				}
			},
		{
			module: "calendar",
			header: "Feestdagen en agenda",
			position: "top_left",
			config: {
				maximumEntries: '10',
				timeFormat: 'absolute',
				urgency: 0,
				getRelative: 0,
				dateFormat: 'D MMM',
				fullDayEventDateFormat: 'D MMM',
				fadePoint: 0.50, // Start on 1/4th of the list.
				calendars: [
				{
				symbol: 'calendar-check-o ',
				url: 'https://www.mozilla.org/media/caldata/DutchHolidays.ics'
				},
				{
    				symbol: 'flag-checkered',
    				url: 'http://localhost:8080/MMM-Formula1/schedule.ics',
				},
				{
				symbol: 'university ',
				url: 'https://calendar.google.com/calendar/ical/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxgroup.calendar.google.com/private-5926e1a950f5588d305e66d8b0af0cfa/basic.ics'
				},
				{
				url: 'https://calendar.google.com/calendar/ical/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxgroup.calendar.google.com/private-754f959bc1afb34da4f5ec42e92b1d01/basic.ics'
			},
				{
				symbol: 'birthday-cake ',
				url: 'https://calendar.google.com/calendar/ical/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxgroup.calendar.google.com/private-2f98381b817baa8eb5bce7f11ac22120/basic.ics'
			},
				]
			}
		},
		{
			module: "MMM-MovieListings",
			position: "bottom_left",
  				// Default module config.
				defaults: {
    				apiKey: 'xxxxxxxxxxxxxxxxxxxxxxxx',
				region: 'NL',
    				language: 'en-EN',
    				interface: 'poster', //'list', 'poster', 'detailed'
    				includeMoviePlot: false,
    				maxPlotLength: 198,
    				header: 'Nu in de bioscoop',
    				moviesPerPage: 0,
    				refreshInterval: 1000 * 60 * 60 * 24, //Once a day
    				baseUrl: 'https://api.themoviedb.org/3/movie/now_playing',
    				animationSpeed: 2.5 * 1000,
    				pageChangeInterval: 30 * 1000
		}		
		},
		
		{
    			disabled: false,
    			module: 'MMM-NOAA',
    			position: 'top_right',
    			config: {

			apiKey: "xxxxxxxxxxxxxxxxxx",    // https://www.wunderground.com/weather/api  select the middle plan... 
			useAir: true,             // set to false if you do not want to use Air Quality Index
			airKey: "xxxxxxxxxxxxxx",    // IF you want Air Quality Index
			pws: "xxxxxxxxxx",         // go here to find your pws: https://www.wunderground.com/wundermap
			showClock: false,           // Hides or shows clock
			dformat: false,             // for M/D/YYYY format, false for D/M/YYYY
			format: "24",              // 12 or 24 hour format.. will default to 12 hour if none selected.
			ampm: false,                // to show AM and PM on Sunrise/Sunset time
			showGreet: true,          // deafult is false - to show greeting under clock and above date
			name: "xxxxxxxx",                  // Your name
			showWind: true,
			showDate: false,
			showForecast: true,         //show bottom 3 day forecast
			flash: true,                 //Today in forecast flashes halo
			showUV: true,               //show UV index
        		showBar: true,             // show Barometer
        		showHum: true,              //show Humidity level
			position: 'top_right',       //whatever you have in above position must also be here
        		alert: true                //show weather alerts default is true
		}
		},
				
		{
        		module: 'MMM-Formula1',
        		position: 'top_right',
        		header: 'Formule 1 Classificatie',
        		config: {
			maxRows: 6,
			season: 'current',
        		calendar: true,
        		fade: false,
        		fadePoint: 0.2,
			grayscale: false,
            		// Optional configuration options - see https://github.com/ianperrin/MMM-Formula1#configuration-options
        	}
    		},

		{
			module: "MMM-ImagesPhotos",
			position: "bottom_right",
			header: "Onze reizen door xxxxxxxxxxxxxx .................",
			config: {
			opacity: 1,
			animationSpeed: 5000,
			updateInterval: 50000,
			maxWidth: "100%",
			maxHeight: "100%",
		}
		},
				
		{
			module: "newsfeed",
			position: "bottom_bar",
			config: {
				feeds: [
					{
						title: "Algemeen Dagblad",
						url: "http://www.ad.nl/home/rss.xml"
					},
					{
						title: "Telegraaf",
						url: "http://www.telegraaf.nl/rss/"
					},
					{
						title: "Trouw",
						url: "https://www.trouw.nl/home/rss.xml"
					},
					{
						title: "Volkskrant",
						url: "https://www.volkskrant.nl/nieuws-voorpagina/rss.xml"
					},
					{
						title: "Nu.nl",
						url: "http://www.nu.nl/rss/Algemeen"
					}
				],
				showSourceTitle: true,
				showPublishDate: true
			}
		},
	]

};

/*************** DO NOT EDIT THE LINE BELOW ***************/
if (typeof module !== "undefined") {module.exports = config;}

Thanks!
Peter

Nice tutorial!
Time to connect the Pir to the Pi.
Thanks!
Peter

Thanks!
Great help!
I hope this helps.
Next time I will post my error logs here.
peter

@cruunnerr after typing pm2 status I see two processes:
MagicMirror online
mm. stopped

after typing pm2 stop MagicMirror both processes are stopped.
Peter

@cruunnerr , I am very sorry and it sounds stupid, but I have no idea how my MM starts.
I had a lot problems to make its start automatically, but now it works.
I cannot stop MM, only minimalise it with CRTL-M.
SSH does not work (for some reason) VNC works well.
Peter