Which is the best exchange platform to use ??
It all depends on your region, the coins you are interested in, etc...
I personally am using Binance, Kucoin and CoinExchange. The last one, cause it has new coins faster and these can grow a lot when they hit Binance.
I also have an accoint on Cryptopia, but never used it, and I am verifying my account at Kraken, to convert it again to Fiat money.
Same here, Binance and Kucoin for the 'big stuff', cryptopia and coinexchange for the small coins. Haven't ever had problems with any of the above. As a bonus, all 4 still have relatively high withdrawal limits for unverified accounts.