If you are working professionally with TypeScript and have access to egghead.io, I strongly recommend you the Course Advanced Static Types in TypeScript by Marius Schulz. As long as you haven't mastered TypeScript in every detail yet, I am sure that you will learn new interesting features of TypeScript. The never Type, the usage of Discriminated Union Types, and many more topics are covered in this advanced course. Marius does a really good job in explaining them and their usage.
Give it a try ⇒ Advanced Static Types in TypeScript