The best recommendations, in my opinion, have already been given. But I would like to add that my current knowledge is the result of the analysis of several sources of information, and maybe even more than a hundred resources. Think of it as a project from https://ca.papersowl.com/research-paper-writing-service that you only do on your own. Although it would be ideal if it were enough for all questions to turn to research paper writing service. So do one or two courses at the same time, but check all the information received.