+2 +2 -4 +4 -15??? This is functional?
 

I received +2 +2 -4 +4 -15 (3-2 overall) -- do you need to obtain a 90% win ratio to be promoted form silver I to gold V?

Seems unfair since you tend to get a troll every couple of games.

It's your mmr; in the past, you lost many times to silver players, so right now, you're getting matched with bronze/silver V. You'll need to have a decent win ratio to get your mmr up to par, and then you'll be able to promote.

So then I do need about a 90% win? I mean if a loss might remove 4-7.5 wins?

Your MMR will keep climbing even if your LP are not going up. If you go back down to 20 LP but get your MMR to the "approved" value then you will gain LP pretty quickly and not lose as much at all.

You have to consistently have more wins than losses and it will eventually stop clamping you. You have so many losses while in silver that it's holding you back. You have 343 losses, but only 352 wins, until that gap massively increases it will continue to clamp you, as it should.