what should I do if it crashes on launch

[Child]

it says The UE4-FishGame Game has crashed and will close LowLevelFatalError [File:Unknown] [Line: 741] and some texture things I cant remember exactly

[ryguydavis]

Hi there, sorry it's not working for you. We've never seen this bug before but as every computer is different it's definitely inevitable we'll see everything eventually.

I did some digging and found a related crash on another game (I made sure to find a result with both "LowLevelFatalError" and "741"). There is a good chance this is particular to your graphics card, and possibly that it doesn't have enough memory to load in the game textures. Unfortunately they didn't solve the problem either but it's the best lead I found:
https://steamcommunity.com/app/1592360/discussions/0/3377158861980656217/

These seem less related but if it were me I would try what's suggested here:
https://www.youtube.com/watch?v=HmZJApHa3mQ&t=264s