why in these two last days this great dump? I have missing something? Or just people start to exchange waves in btc before Segwit2x fork?
thank you for all explanations and sorry for the dumbs questions but I am not following every day the forum

No you do not missed anything : announcement for NG release was made in such terms that everybody thought it was the official release.
Now they realized it is just the testnet, that they have been maybe abused so they sell, add to this the fact that maybe Bitcoin is back in china, the future fork.

Big problems right now is
-bitcoin civil war
-difficulty to create an efficient buzz in this situation
Just buy more and wait