For Chrome users, you might have a login issue (because your browser keeps an outdated cookie).
Translation might not be accurate.
Right click on the forum page (somewhere without link, image, etc), then click on "Show page information". A menu will open on the left of your brower, click on "Show cookies and website data". A window appears, click on "
www.luclin.de" then on "Delete". Now try to login again, it should work properly.