You can also listen to audiobooks, whoever likes what) How to keep up - the daily routine, allocating time for reading or listening to books in a daily or weekly schedule will help. Now, with the advent of e-books, it is more convenient and easier than it used to be. Online education has received great development recently - there are a number of resources with online courses on a variety of topics. There would be a desire - and there are a lot of opportunities in the modern world!
For example, cosmonauts study constantly and during their time in the detachment they master a large amount of knowledge and skills. They learn almost all the time between flights. The time of narrow-profile specialists is gone. The wider a person's outlook, the easier he perceives new information. The better he will be able to orient himself in the new situation. As my well-known and respected colleague says, two skills are very important for a modern successful person: "ability to see" and "ability to perceive", look and borrow: if some approach works in one area, then it is likely that it will work for you. It is important to be able to "turn your head" 360 degrees. It is not shameful, it develops and enriches the life experience of each of us!
And be sure to get yourself a hobby - a significant number of hobbies one way or another develops our brain.
Good luck with your development!