What kind of problem does my phone have? Is it solely the screen or is it more internal?

I had an iPhone 6 for over a year before dropping it from a height and at the angle which it landed on, the bottom part was very shattered. Prior to and after that, I took very good care of my phone. Got a replacement from ATT's insurance for only $100 which is great but it was refurbished, which shouldn't have yielded a problem but it might have. Dropped it once, and whenever I shook my phone even gently I would hear something moving around inside it like a loose screw or circuitry. Then the screen started to become unresponsive at certain times. Then I started noticing black patches and such as of recently, along with disturbing interruptions where my phone would abruptly bar my control and open random apps and type random things without me doing anything. Today I dropped it directly onto its face, and when I turned it on the screen had many RGB-schemed streaks and giant black patches. It was also relatively unresponsive and the longer I kept it on, the thicker the lines would grow, turning the screen almost white. Managed to somehow make a call to my mom, but it's completely trashed. Also the screen, with frame, has been separating from the rest of the phone for a long time. It's popped off the bottom right corner. Are all these new problems related to the screen or is it more internal? Is it an easy fix like a screen replacement? Or did something happen to the inside?

Added (1). I must also say, when I removed my glass screen protector I was shocked to discover there was barely more than a scratch on my phone's actual screen.

You are right that the phone is completely trashed. Take it to a repair shop and pay $$$
Fancy electronics like iPhone 6 will suffer greatly from freefalls and sudden stops onto hard surfaces. Perhaps you should stick with phones on top of tables, attached with cords? I have used those for over half a century with no failures.