Q: Got Banned for 90 days !

This is a user to user support community. Your best bet is to contact Apple Support directly using this URL and choosing Contact Support in the left menu. http://www.apple.com/support/music/

This is because you are really not supposed to use two Apple IDs like that. Using your friend's ID to download content is misusing his ID. This would allow both of you to have content only logged to one ID on more devices that allowed. The 90 day lock has always been in place too, this prevents you from using multiple IDs.

Get rid of the content with your friend's ID and download it with yours. Then, if you wish to log back in with your Apple ID, then you are going to have to contact iTunes support and ask them for assistance, because you were sharing an ID and the other one is locked. http://www.apple.com/emea/support/itunes/contact.html

Anything that you downloaded with your friend's ID does not belong to you. Those are the things you should delete. Then  you can download them with your Apple ID, and you need to get iTunes support to assist you with getting back into your Apple ID.

I'm guessing that is correct. So long as it describes your problem. You should not, however, put your full name in here. I will ask the hosts to edit that information.

Your not banned you just have to stick with one apple id because the icloud tried to over run your previous account and you cant do that. Maybe setup family sharing. Set up Family Sharing - Apple Support Hope this helps

Don't encourage misuse, Family Sharing is for family not friend(s)