Kallum Williams, Maybe try factory reset one more time. The phone worked when you gave it to your friend, you got it back and did not work, you replaced the screen assy, and still no touch. The phone may have been dropped again before you got it back and damaged the mother board or by chance you received a defective replacement display. You can tear the phone back down and clean all connections(Qtip dampened with 90% or better Isopropyl Alcohol), check all connection pins for damage, look at board for any loose/damaged/burnt components, etc.. Check battery voltage with DVOM while apart also, to make sure it is holding charge. Put phone back together and give it a try.
Turn off your Samsung Galaxy S6 Edge.
Press and hold the volume up, home and power keys together.
When the device powers on and displays (Power on logo) release all keys and the Android icon will appear on the screen.
Wait until the Android recovery screen appears after about 20-40 seconds.
Using the volume down key, highlight the option, (wipe data/factory reset) and press the power key to select it.
Press the volume down button again until the option (Yes, delete all user data) is highlighted, then press the power key to select it.
After the reset is complete, highlight (Reboot system now) and hit the power key to restart the phone.
I hope this helped you out, if so let me know by pressing the helpful button.