Online C# tutorials for 2018

Don't bother. Most online tutorials are written by people who have as little knowledge as the people who are reading them, and are about as useful - particularly YouTube tutorials which are generally completely inept.

Instead, get a course, or failing that get a book (Addison Wesley and Wrox do some very good ones, as do Microsoft Press) and follow it all the way through, doing all teh exercises. You will get a much better result.