Wait until you deal with code by university educated engineers who follow the rules of software development to the T. Design is emergent. If you see 5 different functions doing the same thing it sounds like you should go refactor it. Private variables that are unchecked? OMG, you might want to add a few asserts and a couple tests. These problems sound insurmountable.

It sounds like you're dealing with production code that makes money, probably so much that they can afford to pay you to improve it.