What exactly do you mean by selling tokens that resulted in losing all of them? And which exchange were you using? So far, I have been using at least 4-5 exchanges and I have not encountered a similar problem. Is it really the exchange that has the problem? Or perhaps it is in your individual account? Please use 2FA and change your password regularly. You might want to try Bittrex, Cryptopia, Binance, KuCoin, HitBTC.
I guess he's using a scam exchange that would usually suck up all your balance. Or he misused and not read the terms of using the exchange. The OP is somehow unclear on what was the issue about his tokens and the exchange.
What you have in the list of exchange are the best exchange that could be recommend to someone who's looking for a good one. But, for them to be aware, even the best exchanges may encounter certain issues. So, issues with exchanges is normal, but the best one could give you a quick response from the team while resolving it.