You can make more money if the market drops because if the altcoins and bitcoin are decreasing you will get a coin with a low price.
But possible also to lose your money once the coin that you bought during dumping are decrease more.
Yup we can but it's very difficult to make a profit when the market is in red. You must have good analysing skills to pick good altcoins to trade then only you can make a profit or else you will lose your money and if you want to recover your lost you may have to wait for long time.