Make 16 square meter room operable for two persons
Not possible if he's talking on Skype.  You two need to sync your sleep schedules, and that's that.  You'll need to address that with your parents.  

The more sensible option, frankly, is to move the gaming PC to commons space (not bedroom), at which point brother will move too.  Having a PC in a shared bedroom is an outrageous situation.  Bedrooms are for sleeping, especially when they're shared.

These are all "parent-involved" solutions, and I gather you're reluctant to go down that road. Okay, then. If your brother wants to keep parents uninvolved, then he's gotta take the initiative to fix it.  He won't want to, of course.  But your brother is the vulnerable one here: your parents could take away that gaming PC just like that.  So if he wants to protect his gaming privileges, he's got to do the heavy lifting to solve this. 

What about "narcing" or "telling on", the discouragement to go to authority figures?  OK, that's the school-yard bully system.  That trains you in life for one thing: the prison-yard bully system, and that is where you'll go if you train your brain to operate in the world that way.  Seriously, what happens if your customer wants you to fix problems with the electrical work they just paid you to do...  Are you gonna call em a dirty narc?  Take their lunch money?  Beat em up?  That doesn't work, they'll call your licensing board, and if necessary, the cops, and you won't be an electrician anymore.  And without that, how do you plan to provide for your family?   You don't.   So you say "Oh, I'll just magically switch to professionalism when that day arrives" - nope, real world, people don't rise to meet challenges, they fall back on habits or training.