gmail account troubles

[Andreas Hencke]

Am Samstag, 1. September 2018, 11:14:36 CEST schrieb Ianseeks:
> Make sure your Authentication is not set to GMAIL - mine uses PLAIN in order
> to work.

In my case “auto detect" and “Authentication” are greyed out so I can t change 
anything. Even the password is greyed out (there are only lots of dots 
visible) so that I' m not able to retype the PW.

How to change that? Or do I have to delete and reinstall the gmail account?

Regards 

Andreas