You have a bit older technology phone and Android has came a long way in the last 2 to 3 years. Your phone was released with Android 2.3. There are upgrades for that phone for certain markets to Android 4.0 (but I would think that phone would run very slow on 4.) Bottom line is that phone needs to be as "clean" as possible to get the best performance.

With that in mind, I would backup my contacts, photos etc., reset the phone and start over. Once it has rebooted, before you start adding your contacts, email etc., I would disable and/or uninstall everything you don't plan to use. Then, and only then, would I sparingly add your accounts and data. Don't use or run any app you don't absolutely need.

That will give you the best chance for success with any gremlins you've been facing.