Let say I have 10 btc now in my own wallet , then on 1 august I got 10 Bitcoin Cash right ? at that tim bcc value $200 , so if i sell my 10 bcc that means i sell my btc too at $200 ? then i lose my both coin just for $2000 , am i wrong ?
Depends on wallet wheather you will get 10 BCC if you change you wallet to BCC one. But let us asume that you get 10 BCC with appropriate wallet then
You are 100%
CORRECT 
If we are talking about exchanges it will happen automatically. That is why i recommended to use different exchange (and/or) account
HOLDING 0 BTC when dealing with BCC
If this is the scenario then it is going to be a huge loss to investors who invested more amount into Bitcoin. I think the majority of the people are not showing any interest in splitting to Bitcoin Cash. I think it's better we have to convert them into different other forms of currency like ETH, ETC, Steem etc.