Yesterday I updated something through the MacBook Appstore. I really do not know what I was updating exactly. I only know it was in the AppStore. It could've been an update from High Sierra to Mojave. I'm not very sure but I think it completed as the red notification badge was gone already and I quit the Appstore. I didn't do anything Special before and after that. Apps I was probably using are: Finder, Safari, Whatsapp, Todoist, Preview...
When I was finished I turned it off and the next morning I turned it on again. The Login page appears and I put in my account Password. The bar then proceeds to load but when reaching about 60/70% of the bar the MBP suddenly boots into a mode which resembles Recovery Mode. There a window reads
"The macOS Installation couldn't be completed." In the Background there is an app/Window opened called "Installation Log/Installer Log". This is why I think the main culprit is the update from the previous day.
I have saved the logs (.txt) (only Errors, Errors and Progress, all logs) of my latest attempt to log into my account. These can be found on my dropbox. I can upload them to other Services as well if needed.
Thank you for your help!