Ok, let's start.

SET C
Setting: post-apocalypse/space opera.
Theme: wacky overcoming-inner-demons story.

It's all about people, who have sth with "First Sign" (It's like a big boom in entire outerspace). Few people survived, and there is no goverment or law.
It's like Water world; small villige in space.

Main characters are "I was a bad guy who made that shit and now trying clean mess"

In every game is some space colony with own problems, and them MC comes. They trying to resolve problems, but main OMG is Second Boom, what will destroy that colony.
Only way to avoid that is to say to about his (or there) sin/s.
But if any MC will sad that too early, they(others people)  will bring them down, for revange.

So game is about trying to solve messed situation, with time runing.

Jacek,

Well, I'm afraid you might encounter some communication problems after all. If there's enough time I can help you edit your game - but I'm worried about the feedback part. This could be a good language practice for you, if you try hard enough and brush up your grammar (plus, we need to find you some good online dictionary and thesaurus, I suppose).

Could write some more how all this will be resolved mechanically?

Only have one piece of feedback

concerning

Main characters are "I was a bad guy who made that shit and now trying clean mess"

Part of the character creation process might touch on how they caused it/why they caused it. They needed medicine, without realizing the truck was carrying a bio hazard, or red lined the engines while activating a hyperdrive unaware of the physics equations.

Of course, given the size of space, causing a galaxy wide disaster is extremely difficult - aside from blowing up stars or letting lose with a couple dozen Relativistic Kill Vehicles (RKV - think Sabot Armor Piercing rounds from hell.) As such, You might want to look at a slightly smaller apocalypse - [planet wide devastation is pretty easy (nuclear war, engineered plague, rocks from space, massive currency disruption)

As to galactic proportions - bringing down the network of gates/wormholes/jump ships etc. that makes Super-luminal travel possible is one of the biggest I can think of.

A possible weird twist to the game: perhaps the main character is Patient Zero (first documented case) or the one at the epicenter of the blast. They are somehow back from the dead to try to fix things, and are thus quite literally dealing  with their demons.

Hi guys, thx for feedback but I hace bad news. I can't continue making this game because lack of time.
Thx for all and I wish you good luck in this "challenge".