I would suggest Mark first looks at which users are hogging the server space and send them an e-mail politely suggesting they look at deleting their unused content.
I have just forgot to say I also imported my favorite book written in English (with audio files),in which I listen to and repeat phrases again and again.
I think what we will do is as follows:
- allow all members to upload and share unlimited lessons and earn points from this activity
- restrict Free members to 5 private imported lessons
- delete all private imported lessons of Free members that have not been opened in the last 60 days. Paying members can import as much content as they like.
Sounds nice to me 
I have just shared some contents of VOA word book for beginner1. I continue to do this activity. Learning only words is not good way but I am sure these contents help me a lot.
Learning only words (even if example phrases contain the new words) is not a good way but I am sure these contents help beginners understand daily news.
Sorry, I forgot to say something on the phrase.
I have just shared some contents of VOA word book for beginner1. I continue to do this activity. Learning only words (even if some examples are given) is not a good way but I am sure this book also helps beginners (like me) understand daily news. (Actually, in the VOA section, I don’t find some contents for beginners, )