Hitting backspace clears the screen

[GogoFox 0]

Hi,

So I'm trying to make a simple p2p(?) chat client and i got a weird bug.

When I'm writing the messages appear below but when i hit backspace while something is typed all messages disappear.

Then next messages are written below the deleted space.

Why is this happening and how can i fix it?

Code:

https://pastebin.com/iPNymcP7

(engrish bad sorry)