I use only one exchange for tradinga and it's Bitfinix. There are all sets for trading and i think it's most safe exchange.
Bitfinex is definitely not the safest exchange right now. You need to pay more attention and read up regarding what's happening with Tether.
Tether and Bitfinex are the same company. Tether's marketcap has continued to fall as people sell en masse. Bitfinex are having to cash out huge amounts from their cold wallet to cover these funds. There is $2 billion of outstanding Tether, and only $800 million left in their cold wallet. They are essentially insolvent right now.
Keeping your funds on Bitfinex is risky right now.