tnx for answers!
I did the change
quota_rule2 = INBOX.Trash:storage=+100M
and updated Roundcube to 2.0.1 and now Roundcube works, thanks!
But cannot send email correctly.
the geht-nicht.org is hosted on another server with i-MSCP by another Provider. It's a valid account which normaly works fine.
But when I send a mail to funktioniert.de, which too is hosted on another server with i-MSCP, but by the same provider, it works.