I was getting tired of the mtp throwing errors half the time, the directories loading two minutes (not exagerating), the copying taking taking hour, so i said screw it and made my own file transferer that uses ADB, which doesnt rely on the slow as MTP. I made it primarily for myself, but since i already made it why not share it :D
From my testing (over USB 2.0) of copying 8.4GB pictures folder, with my app it took 4m08s, approx 286Mbits/s. With MTP, it was showing it will take hour and 3/4, aprox 10Mbits/s
https://github.com/T0biasCZe/AdbFileManager/releases

edit: To go up a directory, double click the list header!

changelog v1.1:

• Added ability to go above /sdcard/,

• added text to double click header to go up

• added pc2android copying

Video: