I know that in this era we no longer recommend books, but, get the book “Working with Legacy Code” by Michael Feathers for ideas and approaches here. It’s hugel

I know that in this era we no longer recommend books, but, get the book “Working with Legacy Code” by Michael Feathers for ideas and approaches here. It’s hugely helpful. It won’t solve all the problems (that’s on you) but it will show you starting points, give you hope, and show lights at the end of the tunnel. It’s a bit focused on testing and moving to TDD, but don’t make the mistake of thinking that’s all it offers.