I was in a school with one of my friends and then he said something that didn't make much sense (and I've never been to that school I saw in my dream)
So I thought out loud and said: "Hey, this is a dream" and the dream started vanishing around me and I woke up.

After I fell asleep again I had other dreams too but I don't really remember them

I only remeber a part of one of them: I was in a person's POV and it was like I was inside a stream, and that person was inside a game called "Signal simulator: Voices of the void"
 (I prob got this dream because I've watched Vargskelethor Joel last stream he made of this game recently)

For context for this next part, there is a console inside the game that you use to check things in the game,
and there is a secret command called "alien", if you type that in the console it echoes "Behind you" or something like that
 and spawns an alien painted in a wooden "thing" behind you 
(sorry, I don't remeber what this is called in English)

So in the dream people in the stream made me write that into the console, but instead of happening what I just said,
the screen got all red and it said something like this: "He is out there, run" after that I sarted running but I don't remeber anything after that