How is the fastest man of the match calculated?

It's actually pretty simple to tell and hard to do (and expensive).

Supported games have a bunch of cameras in the stadium to record the game from several angles. Computers can form a 3D image from the data provided and calculate the distance the players moved between each frame. And if you have that you can calculate the speed for each individual, even the ball. So yes, every player can be tracked individually.

You know the distance and you know the time elapsed: Speed = distance / time.

The hard part is to assign the data collected to the correct players. This is usually done manually, because computers won't always be able to distinguish between players too close to each others (e.g. after goal celebrations).