Thanks for your help. I have the following question now:
How to add a css class to the (manual) excerpt text at the blog homepage? By "manual", I mean that I always manually add the tag to create excerpts.
I also want this css class to be present on single-article pages, so that in general all text until the tag is displayed in a different css class then the rest of the post, for example in .excerpt.
Thank you in advance, hopefully you understand me :D