Hi sören35,
welcome to the Apple (user-to-user) Community.
Re: "I have problem with Safari, i get "spinning wait cursor" most of the time and it is hanging.
I have to force quit and restart Safari".
Things to try:
Check if the Mail app is working ok ... ie: determine if the wi-fi connection is operating ok.
Quit Safari. Restart your Mac: (Apple Menu > Restart) wait for Mac to start .. then log-back in, re-open Safari and re-try. (ie: will delete temporary files, re-establish connection, etc., ... can often clear the way. )
If hasn't helped:
Try turning off any third-party (non-Apple) software, like unnecessary add-blockers, virus-checkers or the like, even VPN can cause interference. If an offending app is discovered, remove app by using the uninstaller from the developer. If no improvement: Also try with any Safari extensions turned off.
If still not working:
Browse through Apple Support's article: what to do:
If Safari doesn't open a page or work as expected on your Mac - Apple Support
More info:
Safari troubleshooting on Mac - Apple Support
More support (online chat, phone, eMail etc)
Safari Support website: info / support / contact:
Safari - Official Apple Support
All the best :-)