Thanks for your reply.
1. The images are optimised. Especially the backend is really slow. Right now I’m using a minimal setup with just the plugins provided/suggested by your theme. The only plugin added is WPML.
2. I’m planning on using WooCommerce. I would just like more control on where the menu items appear – also for the mobile menu.
4. Yes.. Same for a category page.
5. (new) A new problem has shown up: Sometimes when opening a page in the backend editor, it is showing source code rather than the page. See http://www.bodyparts-photography.de/prob1.PNG
Thanks again. Guenter