I used Binance and Huobi, both platform has high trading volume and friendly customer support, if we have any question just contact them via telegram and they will answer just a few minutes later. Both platform also listed good coin and friendly trading interface.
These are my two favorite exchanges because most of the currencies listed in these 2 exchanges have very high trading volumes and the price of that coin is always stable, which makes us more more choice in long-term investment. I personally prefer to exchange Huobi because they have very good customer privacy policies and always have many rewards for their exchange users.