why after price Back to 5,500 back again to rise (Must price Down Because many sell BTC to get BTG)
Because BTG's impact on the BTC price was heavily exaggerated and outside of Bitcointalk very few people even cared about the BTG fork. Arguably not even on Bitcointalk many people did.
I sell half of my BTC when price 6,000$ and was thinking price will Down to 5,000$ after new fork BTG start (till yesterday this was right)
Sorry to say, but price assumptions are not right until they actually occur. Take this as a lesson that markets, especially BTC, are not as easily to predict as one may assume
Yet again, who knows? BTC may fail to break USD 6000,- and drop down to USD 5000,- after all. I wouldn't dare bet on it though.