It's been an year since i stopped typing for fun. Now, I could not say whether my speed has increased but sure there is a change, and I can feel it in my arms.

My tip to improve your typing speed is to
...
Keep typing until you fingers says " Please, stop for today".
Do not think about speed, because speed will automatically follow you once you start typing correct.
So, focus on typing correct rather than speed.
Quantity over Quality.

What really helped me improve my typing speed is typing every day.
Practice typing each day and you will improve.
That is the only way to fast typing.
I started at very low speed, and now my avg is 50