One of the best resources for the private certificate written exam is Prepware. They have an app for mobile too. It’s paid, but it’s the most comprehensive. They even have a subject-by-subject breakdown of questions for you to study so you can understand stuff well.
If you’re looking for a free resource for practice, there’s also http://www.exams4pilots.org/ - but that tends to not be updated as regularly with the latest questions.
If you need any extra help, feel free to message me as well! I’m an FAA Advanced Ground Instructor, and I’d be happy to help you with any questions or doubts.
Good luck, and see you in the skies soon!