Why does my survival world server keep resetting?

Inviting friend to my game doesnt work for some reason.

So I find out about servers and happen to cross to leet servers, I made a server using this leet (https://play.google.com/store/apps/details?id=cc.leet.survival) note there are 2 leets on playstore

The Problem:

The problem is that whenever I go off for a day the survival world resets! like everything me and my friend made on the surviv server is reset and when I join the serv the seed is changed. Help how do I fix this? I really wanna play survival with my friend.