Hello I dont understand I bought for 4000 Eur one hour ago of Ethereum when it was going up, it stayed around the 10-20%, it started to decrease 5 minutes ago so I sold it and now cex.io just gave me 3500eur for it... wtf...

The %came from me watching livecoinwatch.. Cex.io doesnt have the accurate price ??
Values do change every period, and as a trader, you must keep an eye on that. You lose on the trading because of the absence of patience and learning. If have that attitude would not forfeiture once more attempt to be patience and resourceful important about cryptocurrency would you like? The other reason is panic selling. It seems like you are suffering a loss in trading because you are affected by the condition, and you feel freaked when the price goes miserably.