battery – Macbook resetting itself when playing a game

I have a problem with my MacBook air and I need help.

So I was playing Heart of Iron 4 on my Macbook air and all of sudden, My Macbook restarted itself.
I restarted it and now I have this annoying fan sound playing all the time and my battery percentage disappeared, I went through the setting to enable “Show battery percentage” but it keeps disappearing after enabling it.

Can I fix it myself or do I have to go in-store to fix it?