Hi Cat0091,
From the info you provided via PM it is tricky to tell what could be causing this. While I understand you are unable to get the internet speeds, and are able to install or download items via the store and play other games, all of these, including other games, have different demands on the system, which is why even if players are able to download or play other games, we still ask for internet speeds. One of the easiest ways to get the internet speeds is via speedtest.net or a similar site. If the issue is not being able to get the speeds while playing the game, speeds without can give a good ball park too.
Would it be possible to also get the internet details for your friend? and while you say you both can't join multiplayer at all can you confirm if this is only with each other, or have you tried random games online too?
As I mentioned in my original PM, the area not loading could be a separate issue, does this occur as a client or as a host? If is a client it is likely the world struggling to load in a game. If it happens in your own games or private games, it could be a seperate issue. If so, please describe what occurs in detail - any screen grabs are much appreciated to help us get a sense of the gap that is being created.
The game spawning you back a few steps can occur when the game crashes as the game loads a backup of the save (there is a save every 30 seconds or so)
I mentioned it in the PM also, but had you seen this post?
https://7daystodie.com/forums/showthread.php?48737-Known-Issue-Multiplayer-Disconnection what kind of workarounds have you tried so far? Also have you tried broadcasting the wifi from another device or connection via a mobile connection? this can help narrow down if it a particular connection, or if it is a more general issue. Similarly bringing a console to another connection, though not ideal, can help test this. A number of players have found broadcasting wifi so they're not connection directly to their router can help them connect to games.
Kind regards,
Clare