Why does my iPhone keep freezing? - 1

My iPhone has been freezing lately ( it's the 4S )

I don't know if it's just my messages but I've been out in a group chat with all my mates and it's constantly freezing

Don't know if that's it but yeah please help

Added (1). Thanks mate

Hold the lock button down and the home button at the Same time for about the seconds then when you see the apple logo appear just release the buttons and let the device boot back up.
After the device has booted back up hopefully it will start to run like it should? If for some reason it doesn't though please come back and ask the question again and I will try to help you out further.