If i change the default locale for my site under "stores->configuration->general->locale options" it destroys my frontend, almost all pictures and design are removed and only text + product pictures is shown.
If i change back to English (us) everthing goes back to normal.
How do i prevent this from happening?
Did you deployed the static content after the configuration change?
Sorry for the late answer.
No i did not.
Thanks for the help it is working now.