Sometimes exits 4 no reason,me and my friend can't play online multiplayer,load generation slow

It often crashes and when I go open the world again some of my builds"magically disappear"
How can me and my friend play online multiplayer? I already invited him in my XBOX account and invited him to my survival world but his screen just says "unable to connect to world" a multiple times already.
World generation takes more than a minute or too