Making games. What to do after learning C++

Hi, I've just finished learning C++ and SDL. But... I don't think i can make any good 2D game like that. I've heard about desing patters, and OOP but they are too hard for noob like me.

I've been using unity. It wasn't hard i didn't need any tutorials to do stuff. I should change a question a little.
I'm looking for a proffesional way to code good 2d game engine.