When my fingers hurt after too much time on the keyboard, I readjust my sitting position. Sitting is not a normal trait. Take a break, and get the blood flowing again.

What really helped me improve my typing speed is to accept that fact that I personally do not know where the keys on the keyboard are but because I practice to allow my muscle memory to react quicker

My tip to improve your typing speed is to take your time and go for accuracy and not speed