iPhone 4 very slow and lags a lot?

[Visualvolcano914]

I have had my iPhone for about a year and over the past week the internet, games, and texting all have become slower. The games lag so much that you cant even play them. I heard that if you delete some unnecessary things your phone will return to original state. i now only have two apps that do not come with the phone, subway surfers and Instagram. i also have very little music and deleted a lot of photos.
Is my phone dying and going to stop working? Is there a fix to this? will it remain like this until I get a new phone? please help!! thanks