@leocg
Problem solved!

The extension "ImTranslator" was the problem. There it is automatically set that ALTGr +Q leads to the deletion of the entered data. You can disable this setting in the options.
Thanks.

After entering the @ sign on any page of the browser (in the context of the e-mail address), all data entered on this page so far will be resolved. However, if I previously copied and pasted the character, nothing happens.
If I delete all cookies, the problem goes away. Then back again. The problem does not exist in Firefox, which can be used as an alternative.

What can it be?

Starter22