i am using cex.io for few days and can someone tell me how is possible to price of btc drops and price of ghs rises. sorry if question is stupid but that not looks logical to me. thank you in advance.
Well, one school of thought is that since BTC value is dropping, mining is less profitable, so GHS price should drop too. I think that's what you describe.
Another school of thought is since BTC value is dropping, it takes less fiat to buy a GHS. So instead of it costing $6 for that GHS, it's now costing $4, so the price of GHS goes up to compensate.
You could say the truth is somethere in the middle, but as it has already been said logic and rationality rarely seem to enter the cryptocurrency world.