My iphone isn't working AT ALL
So i was on my iphone 4 on the app instagram.suddenly the instagram screen turned black but i could still see my Wi-Fi, time, and battery icons up top. I tried to exit the app by pressing my home button but it didn't do anything. Then I tried to turn my phone off but it wouldn't turn off. THEN I tried to lock it by pushing the lock button and the entire screen went black, but it didn't go to lock screen. I pressed the lock button again and it went right back to the black Instagram screen. My phone won't do anything except stay on that screen and I'm like freaking out so help As soon as possible!
Added (1). And i also force restarted it already and it wouldn't do that