I'm not a front end dev but am an experienced programmer. About 3 years ago I took a few evenings and to work through Angular tutorials - at the time I didn't realize these new frameworks rendered client side.

After I had a few things on the screen I added Bootstrap and started to learn CSS from scratch.

My advice is pick a framework, I like Angular 2 ( or any batteries included framework) and just work through the tutorials. Type it all out instead of downloading the starters. It helps if you have an idea of an app to build rather than just banging out Todo apps, you can then apply what you learned to a project that means something to you.