Unable to update

i have an iPad 2, 16 GB it worked well until recently.

• I am unable to download an app: when the latest iOS version 8.3 came out I thought this would fix the bug but not so fast.
• I have not been able to update because of storage space. my iPad is showing used capacity of 12.4gB. When I tried making space by deleting some videos, photos and applications in order to free up space for iOS 8, this did not adjust the space instead it shows that I have "0" bytes available and I no longer see the applications I deleted.
• After deleting the files I noticed that i can no longer launch mails. When I click on mails the screen automatically returns to the home screen.
• I also tried backing up in iCloud's to free up more space but I am unable to do that as well, when I tried it return to settings.

I Do not want to reset because of fear of losing my info. I tried to do a backup but as mentioned before I cannot do that either.

The only thing I can do with my iPad now is to use safari with limited access.

WHenever i I launch some sites it does not load or a I get a pop us asking if I trust the site. I never had this issue until a month ago when the iPad started acting up