Nextcloud view after login incorrect

hi nextclouders,
after upgrading my nextcloud server (ubuntu 18.04, nextcloud currently on 19.0.4), the web-view changed in a way that working with nextcloud is impossible. the view looks like optimized for mobile phones, but i’m using a normal pc with firefox or chrome or whatever. a solution is to log out the user and make a re-login. after the second authentication, the web-view change to normal view and nextcloud is usable again.
i’m adding 2 screenshots where you can see the difference between first and second authentication view.

  1. screenshot = view after 1. login, solution to log out the user
  2. screenshot = view after 2. login!