since nothing was really working, i gave in and fired rm -rf .git
maybe a bit drastic and i am loosing the whole commit history, but i have to finish the project. In this state i wasn't able to commit anything. I saved some copies and will have a deeper look trying to understand what has happpened
git checkout 5b001a2
is working, but the error persists
git status
error: inflate: data stream error (incorrect header check)