Hello.
- Soft reset your Mobicel retro: Press and hold the power button until the phone restarts.
- Uninstall unnecessary apps to free up your internal storage.
- Back up and reset the phone to factory default.
- If the phone is frozen on the start-up logo (Mobicel logo) then you will need to reload the it's firmware. See instructions here http://www.satechhelp.co.za/10361/Download-Flash-Rom-Firmware-Mobicel-Retro