Hi Ashish and welcome to Android Forums!
There are several things that can cause low memory:
1. You have too many apps installed on the phone.
2. The app caches are large and need to be cleaned out.
3. Your call log goes back to the beginning of time.
4. You still have every text message ever sent to you.
These things reside in the phone's system memory, not user memory. To help, I suggest the following actions:
1. Go through and uninstall apps you no longer want or need.
2. Clear the caches. I suggest
Clean Master for this task.
3. Delete your call log and start over.
4. Delete old text messages that are, for example, over 2 weeks old. I suggest
SMS Cleaner for this task.
Hope this helps. Let me know if you run into trouble or have any other questions. And do visit the Galaxy S2 forum: there is one for each major provider and the GSM version.
It's great to have you here
