It's only a temporary situation, after the fork the price of bitcoin back to grow up and the price of BCH go down
We only need to wait, bitcoin core it's the only one, don't lost trust on it and hold bitcoin
Bitcoin would not instantly dump, it might show sudden change but its a normal thing about bitcoin, its volatile. It changes from time to time but definitely going to rise in value. Bitcoin cash would never be a threat for bitcoin, its just a bubble making people panic and attempt to make people switch with it. Suddenly, bitcoin is so established that no one could ever manipulate its value.