I see, you want that that Lamorghini, well if you really want udemy is always a good start. Personally the difficult part for me when learning a new programing language is not resources, it's the motivation to keep do it and I usually need a real project to work on. (10 years + dev)
Usually you find on github "awesome-XYZ" repos (ex: awesome python, awesome c, awesome go), but for cobol, most of the projects are dead
