This could be the most constant myth that we can hear around Bitcoin Cash, and is that the price of the BCH depends exclusively of the BTC performance, and this is not true at all. Even though, BTC is the most dominant cryptocurrency available in the market, and if it goes up, or down that can have an effect on the other currencies such as BCH. The effect is sometimes positive and sometimes negative it just depends on the market and it is hard to predict.
Yes it's true that in this moment, the crypto market and it's prices depends directly from the performance of Bitcoin, but Bitcoin Cash price does not depends more than the others. Also, it's true that when 1 coin does it well in the market, it's common for crypto investors to take their money and spread it around into other coins, and this is one of the main reasons why all the coins gradually go up together or down together, but this does not necessarily mean that the BCH price depends only of the perform of BTC.