Don't worry: your rating didn't reduce.
There are 3 different ratings for live chess: Bullet, Standard, and Blitz.
What seems like one going down is a different one going up.
You'll get the hang of it soon enough 
My Rating!!!
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You play different time controls.
It looks like it went down from 904 to 818 after winning. However 904 is your standart rating and 818 is your blitz rating.
Thnx for help!
Could you please tell me the time range for each rating?
Guys my reduces by the start of every match although I have a 5-0 win streak so far!! Can someone tell me why? Thank You :)