How does one decide a system to resolve conflicts

Hello

I've started to lay out a plan for a homemade biopunk ttrpg. However I'm a bit stuck at the system for determining success or failure.

My one idea is that conflict is resolved by having the gamemaster and player roll dice, add their bonuses/minuses and compare, and whoever has the higher number wins. But I feel like this would only work in combat.

So, how does one decide which system for creating outcomes works best for a project?

P.S. sorry for bad english