Guys help !

guys please I'm in a very bad situation. My computer was hacked last night when I was downloading a normal legal game like any normal game from its own website but the game needs its own emulator and I downloaded the emulator first it came as a setup and I downloaded it on my computer its size was about 250 MB and I let it download and browsed YouTube a little and suddenly while I was browsing! cmd appeared for me in a split second and disappeared very quickly any help