Wix has implemented another great project: Wix Learn
A website where you can train, and this, with videos made by Wix itself.
For exemple:
Go to a subject and choose " Courses "
I wanted to get started on Velo, and now is done 
It’s free for every personn who now the link 
And Wix has also set up a certification system to validate your skills
For now it only works on accessibility and Velo, but soon others will arrive (like SEO = my passion)
I find it really wonderful to be able to make his courses available online.
Finally, if you are not perfectly bilingual, you can choose to subtitle the courses in the language of your choice.
Thx Wix !
Denis