I don’t know… it should not be an issue today.
When i open your site in Safari i get this error:
Safari can’t open the page “https://aktives-bewusstsein.de/”. The error is: “cannot decode raw data” (NSURLErrorDomain:-1015)
And the NSURLErrorDomain:-1015 error is returned if the a Compress Stream eg. GZIP doesn’t supply the relevant data for the browser to decode it.
With any modern apache/nginx server there should be no issue with GZIP.
But it could be a server setting has GZIP enabled and maybe a cache plugin has it enabled and the two are conflicting.
I would start by disabling any cache optimzation plugins to check for conflicts. If there is still an issue then disable gzip.