Problem opening Inventory or doing anything on Realm Servers

Hey

I'm currently running into the Problem that I can't do anything on Realm Servers. Once I joined I can't build, break or open anything neither the world will load more than one chunk. I tried opening Ports and change DNS Servers but neither worked. Am I the only one with this problem because I couldn't find anything in this direction. All other Servers work fine onyl Realms is broken.

Please Help