What really helped me improve my typing speed is I learned if you have been typing for a while and still make mistakes try hard not to make mistakes. I have improved as much as 5 words per minute just by making less mistakes. this contradicts what I said yesterday but it works.

When my fingers hurt after too much time on the keyboard, I suck it up and drive on.

My tip to improve your typing speed is to practice practice practice. also actually try to move your fingers faster even if you make more mistakes.