is it possible to edit the main page? (add buttons oder icons)
I want to place our logo and a text into these red areas.
You talk about the static slide that appears with the Play button because AutoPlay has been disabled by most browsers, and Captivate adapted to that situation.
There are several possibilities. I tend to use this one, with a poster image and replacing the Black Play button by a shape on the poster image. I think it is more future proof than hacking files which can have to be changed if the browser setup is changing again;
Here is an example: