@billy Hack The Box is about the best challenge site I know for pentesting. You could try playing in CTFs as well, but CTF puzzles may or may not be security related. However, CTF challenges from past years tend to have write-ups available online that can help you learn.
"Secondary school level" CTF: https://picoctf.org/
"University level": https://365.csaw.io/
Find all the CTFs: https://ctftime.org/
A Mastodon instance for info/cyber security-minded people.