Recode and clean up the game code.

I have a chess game that is not well coded as a beginner developer worked on it. I want you to recode it, clean it, refactor it and solve any bugs inside. Even there are some spelling mistakes. There's also some old code inside that needs to be removed and old UI has to be replaced by new UI.

I need an expert in firebase and SOLID principles to refactor the code and fix some networking bugs.