Crashes right afte i start a game.

So i just started a game. Got my favorite lane and champ. Going well, I got the first kill and my team got kills later too. But right after lvl 3 it litterally crashes. i can hear my teammates typing and calling for me. I can see the game nor i can do anything but i can hear the ping and the noise from the game. And i get a message saying the game can't found a file so please reinstall. i tried to uninstall the game but i couldn't even do that because the game was running but i can see it. Then i had to restart my computer. Now i am downloading the game. My match is probably ove rby now and I probably got reported. Can you please fix this BS and get my report out of the system. Why did i crash and why i could hear the game but couldn't see or play it at all. Please fix the BIG bug. I play on windows 7