So the first time I won in a playthrough. I did some quests- "obl urergvpny eryvtvbhf dhrfg", "Ureh frperg vasbezngvba dhrfg",  but my favorite was one "Ureh dhrfg bs  ubhfr jvgu zlfgrevrf". - it was fun

It's a little sad that in the epilogue Xunee qvqa'g ybir zr gvyy gur raq, but oh well she is like that.

But finally I won with about 18 votes.- maybe because I tried quests, but in my previous playthroughs I didn't do any, because I thought I wouldn't pass, but now I tried and to my surprise I did win 3 of them, I hope to do other ones

And can anyone tell me non spoilery what you had to do to marry Kxenia ? 

And how to code your answers ? I tried writing as spoilery-free as possible.

To marry Kxenia -  say you have a crush on her at the beginning. Place her on your cabinet when she comes to visit with Vasily. Don't get engaged to anybody else. Towards the end of the game, you'll get the option to pursue a romance with her.