When I google, I only get results about "user research methods" and these kind of things. What I really want is studies/stats about things like the best position for a navigation menu, best types of menus, color theory... you see? Where can I find those?
https://www.nngroup.com/ is the site you are looking for.
https://www.interaction-design.org/ is also one of the best sites if you are looking to do online courses related to user experience.