[aceracer24]

Settings/system/clear storage is one way.

The other way requires the phone to be off completely so pull and insert the battery. Press and hold the vol down key and the center round key. Now press and hold the power button until you see instructions. If it doesn't work the first time, keep trying. It sometimes take a bit to get the pressure on the butons just right. Just remember that the phone has to be off completely for it to work.

FYI, you mentioned lag when you are typing. This is a known issue. There are "fixes" but IMHO they don't work all that well. It's been suggested that turning off T9 helps, and I can confirm that it does but there is still noticable lag when typing. Your other lag issues are not normal. There is no reason your text should take minutes to show up. Seconds maybe but not minutes.