How to uninstall gmx button

Hi everybody,
some time ago I happened to click a bit to fast on a “yes” button. Now I always have a small button “gmx” on my firefox-window. Clicking onto it a search-site of gmx opens. I want this off but I don’t know how.
I appreciate help. Thanks

How to remove MailCheck for Firefox:

How to remove GMX Go! for Firefox:

If these links don’t answer your question, please post a screenshot of the small button.

Did not work still because not extension for gmx ist shown in the firefox extension list.!
Here is a screenshot of the button I mentioned.
GMX button|488x236

Thank you for answering me.

That simply looks like a pinned tab. Right click it and press “Close Tab”.

Thank you for your answer. This is what I tried several times.yet. But the button ist reopened at once, as it was before. It seems to be an auto-start option but I don’t know, where I can influence this, by deleting.

Mit freundlichen Grüßen

Julia Lampel

Thank you for all answers. I don’t know how, but now everything is fine again. I am happy!