I feel like I have progressed a bit in my understanding of calculus recently, especially because I've been watching 3blue1brown's outstanding videos (who knew the definition of a derivative made so much sense?) but of course, problems are the real test of understanding.
What is a good set of free, solution-provided problems which start with easy stuff (like $\frac{d}{dx} x^2$) and work up to harder problems, ideally with some applications thrown in? There should be a lot of problems; I want to make sure I really get the material.
There are plenty of problems in Gilbert Strang's textbook, available for free here: https://ocw.mit.edu/resources/res-18-001-calculus-online-textbook-spring-2005/textbook/
For even easier questions, the differentiation and integration chapters of this book might be helpful: https://www.biochemtuition.com/wp-content/uploads/2015/07/131310607-Edexcel-Maths-C1-2.pdf