I am a non PRO subscriber. When I try to get a new free course, it says that I am already studying the maximum
The free course limit is the number of free and private courses altogether. The course slot will be available:
1. If you archive one of the free courses.
2. If you delete one of your private/custom courses.
Alternatively, you can exchange 100 rubies in the store for an additional free course slot.
Note: Archiving a private course doesn't release the slot, you'll need to delete it.