I dropped my samsung phone and it is not working properly. What is wrong with it?

I dropped my samsung s5. It fell below 3 feet. I have a case for it but its thin and does not really protect it.

At first the phone was not turning on. The screen was black. I tried holding buttons but that did not do anything. It vibrates a few times though. It turned on my flashlight app light but it went off when I held the buttons. Also, the back button lights up (I am not sure if that is what the button is called).
Then I took out the battery and pressed the buttons for a while it vibrated a few times again. After pressing my buttons a few times, my phone came on. It was working and it let me text for a while but then the screen had that weird fuzzy dot thing & then it went black again.
I took out the battery and pressed the buttons again. IT worked but then it went off.

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