Every level ends with a capstone: a larger project that combines everything in the level. Capstones are the gates of this handbook. Don't move on until you can complete the current one without notes.
Recognizing an idea when you read it is very different from using it on a blank page. Exercises check single skills. Capstones check whether you can combine them into something that works, which is what real data and ML work looks like. Every capstone has a scenario, a list of deliverables, an acceptance checklist, hints, and a full worked solution.
Attempt the whole capstone first. Use the hints if you're stuck for more than 30 minutes on one part.
When you're done, or truly stuck, read the solution and compare it with yours. Different isn't wrong: check whether your approach meets the acceptance checklist.
If you needed the solution for a part, redo that part from a blank file a few days later.
Add anything you got wrong to your "mistakes I made" log.