category description

Dear support-Team, how can I get a category description to look like normal posts do? I want to give each category a dedicated introduction / description. So far I'm using category sticky post plugin but this is outdated and serves only as workaround, example: https://www.stiftung-meeresschutz.org/themen/fischerei/ -> old post is sticky always on top. This should go into the category description. But something overrides all html formatting I put in there and the results looks quite awkward. The website is: https://www.stiftung-meeresschutz.org/ Thanks for any ideas. Ulrich