Applying fonts and font sizes in the composer when writing an article

Hello

I need some help with font changing. I am trying to adapt the font in an article I wrote by marking the respective text in the article and selecting font family as well as size. But after saving it automatically changes back to whatever it wants (or at least that's what it seems to me :-). I cannot make it accept my selections. Why is there the possibility to select font type and size if it does not accept it?

See the article here: http://smartalternativ.com/index.php/de/info/landwirtschaft-garten/bienen-in-not

This does have another style then my other articles and I can't find the reason why.
For other article, see here: http://smartalternativ.com/index.php/de/info/gesundheit-ernaehrung/nose-to-tail-eating

I would like to have a bigger font and also would like to try out the different styles to see which looks best.

Thanks for your help and best regards
Gabriella