Why won't my iphone delete songs properly?

I updated my iPhone 4 to iOS 7.0 and since then my phone has been a pain in the ***. I found out that iOS 7 isn't really suitable for my older phone but unfortunately I didn't realise at the time.

My iTunes is version 11.1.

I'm trying to delete some music as my memory is getting low and there are a lot of songs I don't want. I connected my phone to iTunes and deleted my songs on there. The songs were deleted on iTunes but when I looked at my phone they were still there.

I then started to delete them manually off my phone but after successfully deleting a couple of songs the music app on my phone pauses and crashes.

I turned my phone off and on and also restarted iTunes but it's still the same. How do I resolve this problem?

The music has deleted its just showing you its there, so go to settings, down to music and click it, then scroll down to show all music and slide it across.

There are now several useful third party software options to manage your iPhone media files
I'm using Syncios, the software works quite well to manage my music and avoid the hassle of using iTunes as the file manager. You have multiselect or select all options
You can refer to this tutorial: http://www.syncios.com/delete-songs-from-iphone.html