Hi,
You need to hard reset your phone.
''Be aware a hard reset will erase all your downloaded apps and user data. It will restore the phone to a factory default condition. It will be like when you first bought it.''
Before you perform a hard reset, back up your data using the phone's backup feature.
'''Note:''' If, after performing a hard reset you restore your phone to what is was before you did the reset, using the backup you made, it'' may'' re-introduce the problem that you were having, e.g. if a downloaded app was causing the problem.
If you can, ensure that the battery is charged before you perform a hard reset. Also do not have the charger connected when you perform a hard reset.
Here is a link that shows how to perform a hard reset. (it is not for your particular model but the procedure is the same for your phone)
http://www.hardreset.info/devices/blu/blu-studio-50/