before jailbreak when i was trying to install apps from other sites (which I downloaded them from other sites except app store to my computer) it was starting to install and then it removed, then I thought this is a good idea to jailbreak my iPad so I did it, I jailbreak my iPad 4G IOS 7, and there is an icon named "cydia" on my iPad. which made my iPad acts very weird, I tried to install software from other websites, but this time the software installed but there is an error massage which says "app can't sync", and the icon looks dissolve. I don't know what to do?