Help Needed - Samsung Galaxy S3 I9300 4.3 jb upgrade issue

Hi team,

I upgraded my samsung galaxy S3 I9300 to 4.3 jb on 3/9/14. And from then i am not able to use my phone properly. I brought this phone from UK and now i am in the US. I have the following issues with the phone now
1. The phone is too slow and very sluggish
2. Touchwiz home error is shown frequently
3. Not able to open Gallery or My files ( so that i can transfer my files to the external sd card)
4. Many applications either do not open or open but would be too slow.
5. Lock Screen does not work in between

I cleared the cache partition but still the phone is too slow and these errors are thrown.

Please let me know what needs to be done with the phone. Is there any way i can try to backup my all data in the phone ( i even tried to connect to pc and use kies but that also is not working). Also please let me know how can i do a factory reset?

Appreciate your help in this.

Thanks in advance.

Regards
Jogesh

— modified on Mar 13, 2014, 4:49:17 AM