When I sync my iPhone to itunes it shows over 7GB of "other" files.

Question

My phone has been showing a "full" status and when I synced it I saw that no matter how many songs and apps I deleted, the "other" category kept growing. My brother told me about a trick to swipe the "music" section in the "about/ usage" setting and this seemed to get rid of the "other" but it also seemed to mess up my music player app- it keeps skipping through my songs. 
I have attempted to fix it using this again but it has not worked.  I have over 7GB of "other" files, my voice memos are no longer on my playlist despite selecting it to sync.  I also seem to have lost over 200 songs which will not sync.  I have only ever purchased music via itunes. 
My phone continues to warn me that it is full but I do not know how to get rid of the "other" category.  I am surprised to find out that apple charges $35 to get support.  Wow.
Any help on this would be great, because I seem to have lost access to my music, I've lost important voice memos, my music app is not playing properly, and my phone continues to warn me that it is full.
Thank you. 

Answer 1

I should mention that I also did a restore hoping that would solve the problem but it did not, and it was after this that I lost some of my music.