Is it haram to gain knowledge from buying a course and then sell a similar one?

Assalamualaikum! I will like to know if it is permissible to buy different courses (about digital business) and then mix all the knowledge gained through those courses and sell my own personnal course?
Will it be considered like copying other contents if I do my own video and PDF inspired by other courses even if I add my personal opinion?

Jazak Allah khair! May Allah reward you all the highest level of paradise!