I want to make a remaster of a game

It’s half because of the learning experience and the other half just having something to do if I get bored. I’m familiar with Unity but I suck at coding and structuring the steps involved in making a complete game. Are there any good resources that would help teach me the theory and steps behind remastering old games. Preferably old GBA games. YouTube tutorial links I don’t mind but they tend to suck.