Win 1/4/8 xp lose -28/30xp but why?

Answer 1

adding to Царь СОБАКА - Догго l
And if you are playing with someone who has more xps(higher level) in a specified language then you have a chance of winning more xps usually 32xps. Also losing to them wont make a huge difference in your xps usually 1 loss.
One advise try to experience yourself with what I have said and notice the xps loss and gain.

Answer 2

Jamil Ahmed Chawdhury the rating system is based on the elo system... you can read more about it here
https://en.m.wikipedia.org/wiki/Elo_rating_system
https://www.sololearn.com/Discuss/615039/?ref=app