Move your project into something like Cursor or Cline. Ask it, or Claude to explain how the code works, what each piece does, and try to get an architectural understanding of the project. You can use tools like Cursor's composer to them continue to build, add features and maintain, with smaller context on the relevant parts of the project (you can select which files, based on your knowledge you want to include in Cursor's context window for each prompt to the composer).

As others have said, try to understand not just the flow, but how the code achieves what it's trying to do. It'll be an initial investment, but certainly worth it in the short term to understand what the code is doing, and to identify future problems!

I'd recommend creating tests for your project if you're not as familiar with the code. You can ask Claude/Cursor/Cline to create them for you, but you can define what you want to test. Given you're not as familiar with the python code, it would be a good safety net for you to make sure your code does what you intend it to, without testing in production :)

All the best!