@Tutanota it seem you must have an hidden form somwhere in your top left of the app, all password manager i used put their box here to auto fill (even when logged).

is it possible to fix it in a way password manager don't see it anymore ?

because having to close the box (or prevent autofill to work on the page) is not very cool

What Tuta client are you using and what password manager? We need to reproduce it first.