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 dont understand anything. I want to play survival. There is no open land there. In all the servers i am closed in a building. I can do nothing. I dont know anything about servers and multiplayer. I have been playing only singleplayer till now. Please help me!

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