first match ever...(friendly) and already 2 injuries...?
why?
its a random thing? or there is something wrong with players?

You are lucky. Just 4 days and 1.5 days long injury. Starting teams without Health center can suffer an injury up to 20 days.
I can't tell you exactly how it works, but injury time is depend of players skills, special skills like fragile /resilient, the opponent player and so on.

but umm..first of all - to build a Health center i need to upgrade stadium ?

This is unlucky, even without health center you won't have an average of 2 injuries per match.

Yes, of course i didn't mean 2 injuries per match is avarage, only the lenght I talked about.
You can build your Health center at 13th step of tutorial2, no stadium upgrade needs.

at 13th step?
Intro 15 of 15: Look at us!

im at 15...and still dont have health center...
lol

You just finished the 1st turorial, but here comes the second 15 steps tutorial, and in this second comes the 13th step the Health center, but you have a possibility to build a little bit earlier, after you finished -if I remember good- the upgrade of your training center to the second level.

oh so there is a two 15 step tutorials..
ok then..ill finish the second one when my training center will be finished.

SECOND MATCH EVER AND?????????????????????

Again 2 injuries :)
jejejejeje
2 matches - 4 injuries

soon i will run out of plyers ....

This is getting ridiculous. Yesterday my best player was injured during the cup match (fortunately only for 2.5 days) and today two of my players got injured for 11 days. Add the fact that a couple of my players have red cards and my season is already over.