Support Samsung Galaxy S2 firmware question

Hello everybody.
I have an important question about my S2. My phone did not recognized any simcards and the imei number was just blank as well. So I have found a few simple steps how to fix this. I had to root my phone using galaxys2root and had to download an app called GSII_Repair from Google play to recover my imei. So now my phone is working fine the version number of my android is 2.3.3
There is a much newer firmware avaliable on my phone. My question is can I update my firmware if my phone had been rooted. Thanks

 

Hi and Thank you for your reply. My phone is a UK model GT-I9500 as I live in the UK. When I connect my phone to my PC trough Samsung Kies it comes up straight with the firmware update warning. But it says that if my phone had been rooted it can brick my phone. So I have not started it up yet.

 

Sorry I have made a mistake as I own an S4 as well.But the problem is with the s2 GT I9100.I dont know do I have to try to update the firmware trough kies or not..??