Help NEEDED ABOUT MINECRAFT SERVERS! (URGENT)?

So, i and my friend want to play multiplayer together. So i ttied joining some servers, but they all first ask for registration. And after i register i can play. But i don't understand anything. I want to play survival. There's no open land there. In all the servers i'm closed in a building. I can do nothing. I don't know anything about servers and multiplayer. I have been playing only singleplayer till now.