What really helped me improve my typing speed is... Accuracy and Patience, you don't need to be fast, you will gain fast after you learned how to type very accurate. Because if you are accurate, you won't come back and erase the letters you typed wrong and if you are not accurate and if you just focus on speed, you will keep on coming back deleting the wrong letters you typed in that slows down your speed

When my fingers hurt after too much time on the keyboard, I...

First of all, I go to Youtube and then go here again. You know, it is always just a go and rest, don't take it straight, of course, you need to take a rest or your fingers will be tired and will hurt. That's all my advice.

My tip to improve your typing speed is to...

Always start slow, try not to look on your keyboard, and try to familiarize them. It's better to familiarize than to memorize. Remember, when practicing, do not go fast at first, then just slowly increase your speed when you are familiar with your keyboard. Also, make sure that you are in your right seating position and the right position of your finger on your keyboard. After some time, you will be a fast typist and you will even delete all the error markings.