Again: thank you very much for your reply!
4. (about Hugo templates):
Should I not, in theory, been able to use very template/theme that exists on the internet? I ‘only’ have to add the necessary handlebars?
5. (two post side by side):
Yes, I mean two blocks side by side but both editable from the user interface. Having said this: this is not really important.
7. (mega menu):
I don’t mean a mega menu that’s editable from the GUI but just a mega menu on the website. Having said this: this is also not really important.
8. (about forms):
Thank you for the links with the form providers!