As a beginner, you can slowly add valid TypeScript instead of having to immediately switch to a completely new language.
You can head over to Flavio Copes's TypeScript Guide to get a sense on what TS has to offer.
egghead.io offers two free courses (all others are premium webinars).
Frontend Masters provides another engaging workshop which I enjoyed thanks to the likable instructor Mike North. But you have to be a member of the platform to watch the replay.
Today I found a free React TypeScript course that proved to be surprisingly good: Typescript with modern React (i.e. hooks, context, suspense).
I'm a bit wary of free Udemy courses as the quality tends to be sub-par. There's a lot of noise on Udemy because courses normally only sell for around ten bucks, even though they are advertised at a much higher cost.
But the author of this course, Richard Oliver Bray, did a good job of presenting a practical course on TypeScript with React and React Hooks.
Keep in mind that this is not a course for total beginners, as it assumes some familiarity with React and its tooling (npm, babel, etc.).
It also helps to have an understanding of React Hooks as the author glosses over some of the details of this new technology.
(I recommend reading Robin Wieruch's guide What are React Hooks? to get up on speed.)
Still, I found the Udemy course accessible, easier and more practical than some of the advanced-level egghead.io videos that I watched. It's more of a tutorial and guides you through coding two example React apps.
If you're interested in TypeScript, you might want to give Typescript with modern React (i.e. hooks, context, suspense) a try.
Maybe you can learn something useful. I found the course quite valuable for my level of TypeScript understanding.