You have 512 MB of ram. Regardless of the CPU speed, it may not be able to handle multitasking as well as high end phones.
Solution: Buy a phone with more RAM.
The Commandments of Android
1) Open RAM is wasted RAM - Don't use Task Killers
2) Cheap devices are cheap for a reason. Don't expect high end performance.
3) Boot Loop = Wipe.
4) There are no viruses for android.