Thank you dear Kyle for the immediate answer.
Question One: Just to make sure I understood it right: So I can clone the whole Website and put it in any test-environment, but only on a webserver that is not reachable online?
Question Two: Of course I added !important or tried being more specific in my css selectors, but all this did not help a bit. Therefore my question: is there another cashing mechanism hidden somewhere?
Theme Options-Performance, Swift Framework-Performance I already switched off, Browser Caching, too.
Thanks again
Dorothee