my game says it always crashes plz help

i have just bought this also and it is saying that my game crashed and i have tried on all 3 of my internet and i can't play the game. All i wanted to do is start making some YouTube videos on a modded Multiplayer map that i was going to make for my friends but i can't because of this issue. Please do something about this DEVS.

Hello! We're sorry you're experiencing this problem. In order to diagnose the problem, we need to look at your launcher log file. It's called launcher_log.txt, and can be found in your Minecraft folder. Please attach it to this bug report.