(Soft question?) Sharing knowledge to students, what are the limits?
For actual legal advice, you should consult with your institution's legal department.

Having said that, in most countries, the legal concept of Fair Use protects you from getting in any copyright trouble for normal educational activities. There are limits to fair use (you're not allowed to photocopy a textbook and pass out copies to all your students), but making lecture notes that are based on a copyrighted textbook should be fine, as long as they are tailored to the lectures you are actually giving, and not presented as "here's my summary of the textbook so you don't have to buy it." The exact line where fair use ends is hard to define, and would be up to a judge's discretion if it got that far, but in practice, as long as you don't do anything blatant, you should be fine.