Thanks JSCHERR2000, I think you are right concerning the Adds. I blocked F-Secure, Malwarebytes and a VPN Addon. The grey overlay has gone! The problems with my banking are not over, but you can't solve that. Thank you very much.
When I try to sign in, (FireFox Windows 10) the site opens for a few seconds, then the screen gets a grey transparant cover and I can't do anything. This problem occuts for over a year and the bank (it's where I have an account) can't help. Maybe you...