URGENT - How to Play Better.

I’m extremely annoyed at the moment. 

DO YOU KNOW HOW LONG IT TOOK ME TO REACH 900? Hours. Days. Weeks. Guess what my brother does? Goes onto my phone. Resigns from my account. Loses me 16 ELO which I spent 2 HOURS gaining. It probably looks like to you I’m overreacting. 

I need 900 ELO minimum, and a certain winning streak to stay in my school’s chess club. I’m the lowest rated player in the chess club. I was third. Now I‘ve had an email saying I’m gonna be kicked out if I don’t get back to 918 ELO.

Someone please tell me the best way to get ELO. Best openings, best engine moves. I need it by tomorrow so this is urgent. I don’t have hours to study or play, I have maximum 15 minutes. If someone can help it’s appreciated.