My MM was running now for 48h without freezing. I don’t know what happened the last couple of times. Thank you to @Tribun ! I checked all the logs and found no problem. I will now start to install the first modules and see what’s going on.
Thanks god I solved it!!!
While exiting from /etc/lightdm/lightdm.conf I pressed inadvertently option+x instead control+x and I added “†” in the file without realising it.
Thank you guys for helping me out