500 Error

Everything was working fine I did not do any update or similar and suddenly all I get is:

Oops! Something went wrong
500 Internal Server Error
We will work on fixing that right away.

I can't access settings, not the dashboard, nothing at all, and I am desperate.

I have checked the logs and is a very long file, some of the errors pointing to the database but again, I never made any changes. Some other people are having this error on the cloud (mine is on my server) but somehow must be related. Anyone can help?