In order to get the most secure Bitcoin and other cryptocurrency, I use the crypto exchange Exmo.com it supports Fiat: USD, EUR, RUB, UAH, PLN, TRY. It is possible to purchase: BTC, ETH, NEO, TRX, DOGE, ADA GNT, ZRX, GAS, INK, MNX, XLM, EOS and other coins. I have been using this exchange for a long time and I have not had any problems with it yet.