Hello,
Since the fork we have a new coin very similar to bitcoin , do you think it is a threat to bitcoin?
Now I have those bitcoin cash and i don't know what to do with them.
I don't have the technic gear to choose between both, and I feel bitcoin cash is taking bitcoin down am I right? It's taking a part of its market capitalization.
There are many coins very similar to Bitcoin; most altcoins are just forks of Bitcoin. Most don't copy the UTXO set as BCH did. It could be taking part of BTC's market capitalization; after all, if people are buying BCH (and they seem to be, as there is considerable volume), that's less money invested into BTC. We really can't tell what will happen in the long term, though. I think it's prudent just to wait a while and see what happens. At worst, you miss an opportunity to make more BTC profit. At best, you are positioned to take advantage no matter which coin emerges the winner.
I'm not too worried about BCH as a threat to BTC, personally. 8MB blocks aren't necessary, its developers are unknown and there is no economy built around it.