Facebook SDK login problem on Android

Hi, i have integrated the Facebook SDK to my android app and use it to login. Everyt$$anonymous$$ng works fine. But as soon as the facebook-app is installed on the same device and the user is logged in the facebook app, my app skips the login screen and automatically logs in to the same account.

Trying and trying to force the login screen anyhow to be shown in that case, but seems not possible?!

Has anybody an idea?

btw: I'm using SDK version 8.1.0 and Unity 2019.4.11, but also had no luck with other 7.x.x versions of the SDK...