you can use my template for signup and login
for this you can create videos of your classes and you can use in app purchase , you can make another screen that contains all the paid videos and you can code it like if payment is done then the user can go to second screen else he/she cant
that may not be possible with extension or kodular components , you can use some online service for it
for this use some data base or some online service
you can get idea from the chat apps present in the community
[Guide] Group Chat Application Using Firebase and Google Sheets (Level - Advanced)
for this also i suggest to use a database and some logic