You can take the EDX course: Developing Business Applications with Microsoft PowerApps, CDS, and Flow. Very informative and great trainers. It is free too (not unless you want to get the certificate). Here's the link:
I hope this helps!
The link to the EdX course seems to be broken. It just leads to a giant listing of courses (2,502 of them).
I'm trying this one instead for now: https://docs.microsoft.com/en-us/learn/paths/create-powerapps/
Also, there are lots of great video tutorials on YouTube. Shane Young has a lot of helpful videos!