Crypto market is go down in this movement. I have some USDTs. So I want buy some coins. Is this time good for buy? What are the good coins to buy and Hole long term? Any suggestions? 
good coins for now, of course it's still bitcoin. if you have money and want to invest better to buy bitcoin, the price is currently down. when else can you buy bitcoin at a low price like now. and after that you can hold. and you will get a big profit.