Here you all go, a hopefully useful article from over on Medium.com
about learning Bootstrap V4. I was suprised at the total, complete differences in some things when workin on older themes, ie, Cards
A little basic but interesting as it mentions a new free bootstrap 4 course, coming up (and farms for your email address) and you can follow links off it to to yet another new learn to code and teach coding site
that the article Author hosts