I've never been much for following courses and really the best way to learn is practice. Working with a cloud stack like AWS is a great start. Try to setup a an app server behind a load balancer, CDN (Cloudfront) and DNS (Route53). Read up on VPCs, what a CIDR block denotes. The core functions of these kinds of appliances is actually really simple. Just routing, caching and occasionally transforming requests. The ins and outs of specific products (ie CloudFront vs Cloudflare) is going to most useful and you get that from reading product docs. That and learning to use command-line tools like curl, dig and maybe tracert if you're feeling fancy.