Is solving the problem sets a good way on picking up missing math knowledge?

Hello! I am a slightly older self studying person who discovered this website today. I really enjoy math and have covered both the AoPS counting and probability books. My geometry and number theory knowledge is virtually non existant though, is chewing through the problems in the problem set a reliable way to practice? (As opposed to grinding through entire books). Would appreciate some help fom the more experienced people on this site! Also thank you for making this website, helps people like me who have graduated college long ago to really enjoy and get good at math again.