There are classes on Udemy and Plurasight which are low cost, but not free. I am looking at both and the stuff on Udemy is better.
There are free videos on YouTube and one that caught my eye is Path To Code. It looks pretty current and so far it is as good, if not better than the paid services.
There is a lot of duplication of concepts, but I suppose it does not hurt to hear it a few times.