Battle.net

is it true that getting a promotion is kinda about the amount of games you play?
like a player going 30-0 wont get a promotion cause he hasnt played enough whilst another player going 150-40 will get a promotion?

You get promoted if your hidden skill ranking is stable and matches the hidden skill ranking of the players in the leauge above you.

Imagine you have a coin, Vezus. But this coin isn't even, you are trying to find out whether the coin lands ~50% on one side, 50% on the other, or whether one side is maybe heavier or the shape has an influence on the flip, so maybe your coin will land on one side more often.

You toss it, again, again and again, 4 times in total.

Now maybe you've had twice heads, twice tails, maybe heads came up more often maybe tails.

But you cannot say anything based on that, as only 4 tosses aren't giving you any data.

What can you do? Well, you might toss the coin a hundred times, maybe a thousand times, the results will tell you way more about it now. Maybe it's about even, ~500 times heads, ~500 times tails, maybe not, one of the two might have been tossed way more often, in any case you get data.

And this is in a very basic fashion what the system does. The more data it has about you, the better you can be placed. There are things like MMR, as mentioned by Heresy and this MMR is based on your comparison in battle with another player and his MMR. Are you doing 50/50 against players who have about your MMR? Or better? Or worse?

The more you play, the better the system will be able to rank you.