Cant log into my gamertag

when i try to log in on my account, it looks like im logged in. But my gamertag is Steve, and if I press any button, the game crashes, I have tried reinstalling the game and restarting the iPad. But I can’t still log in. I need to help my friend on his realm. And his gamer tag is MintMangoDeluxe. I will be very glad if you could find a way to fix this. Thank you so much!

/greetings theonlybnoob