Hey Melandre, You best bet on this model is to only keep two or three apps installed, or you can:
1. Hard reset it
2. Add no Google account
3. Only install your apps using downloaded .APK files
N.B Since the phone itself comes with very little internal memory, please do note that the above will only alow you to get away with just a handful of app installations (and that provided each one's size average 5 or 10 megabytes.
You can also use an app called App2SD to move certain apps from internal memory to SD.