I can't play multiplayer

it's impossible to play multiplayer, I can never get into my friend's world all the time I have to use another app to play the problem and it crashes us a lot of other apps so I would like that you solve this problem please it's impossible to play multiplayer, I can never get into my friend's world all the time I have to use another app to play the problem and it crashes us a lot of other apps so I would like that you solve this problem please