C# learning from intermediate to advanced topics

Hello Everyone i would like to mention i have been on and off as a game developer so for me i use both unity and unreal for the games i make My question over here how do i make my decisions while choosing the correct methodology This question is not for single scenario this is to choose the methodology without searching a youtube tutorial. Let's say i want to make a playercontrol i know we can use vector3 for transformation/positioning/moving the player and quaternion for the rotation and destroy.game object for killing an object and i know there are more concepts too integrate but what would be the best way to optimize the code or the language i use exactly to my need and give the player smoother experience

I have tried c# and c++ both while doing my practice but whenever i get an idea of certain mechanics i seriously type the issue in youtube which makes me blindly follow the method and if at all i stuck in something and i again go watch youtube videos which is actually making me dependent on something to avoid these issues can someone guide me how to learn c# or C++ and write the program according to my requirement without following any kind of resources if at all i need to follow ressources which is the best way to follow

Thank you in advance