Jailbreaking voids the Apple warranty and also means that you will not get any support from Apple, including from this Apple forum. Jailbreaking can't be discussed in this Apple forum.
For the slowness:
- Reset the iOS device. Nothing will be lost
Reset iOS device: Hold down the On/Off button and the Home button at the same time for at
least ten seconds, until the Apple logo appears.
- Reset all settings
Go to Settings > General > Reset and tap Reset All Settings.
All your preferences and settings are reset. Information (such as contacts and calendars) and media (such as songs and videos) aren’t affected.
- Restore from backup. See:
- Restore to factory settings/new iOS device.