I also recommend acloudguru, they have very nice courses about Kubernetes and GCP, which provides a very good basis. I especially liked the certification courses - even if you do not pursue for a certification. For example, "Google Professional Cloud Architect" course helps you dive into GCP ecosystem and get very short overview about each of the service (purpose, limitations, specifics).

For anyone, who is very fresh in k8s topic and don't won't want to spent a cent for learning I recommend starting from edX course [0]. It provides a nice introduction and great notes, which you can copy as some cheatsheet. Such cheatsheet will be a definitely helpful hand in first weeks with k8s.

[0]: https://www.edx.org/course/introduction-to-kubernetes

solid. devops person here - these guys know their stuff.