Can anyone help to answer it? because I want to invest for bitcoin cash.
Right now, not even close.
If scaling problems arise again, then there could be some increase in the value of bitcoin cash. But I don't think it will increase enough to pose a threat to Bitcoin.
This. Keep an eye on the fees for bitcoin transactions - if they spike, people may start moving money using bitcoin cash instead. Bitcoin cash doesn't need to increase fees, it can just pack a lot of transactions into big blocks and make money from the volume.