It's quite difficult to pick up a good and reliable exchange but I'll try. To me, it's Changelly Pro. Can't tell you why. I just registered there and don't want to move on searching for another platform.
I still think you should create another big exchange trading account, don't put all your money in one exchange, it will be very risky.
We see a lot of scams or hacker attacks, so don't be subjective because any exchange could be hacked in the near future. You can check out a list of big scam exchanges and hacked issues in 2019 here:
https://currency.com/biggest-cryptocurrency-scams-of-2019Although Changelly Pro is a good exchange, you should also preserve your capital well.
In the end of the day everything comes down to safety and security of your funds! This is the best advice here, don't put all the money in one exchange! There're many good exchanges, but all of them can be hacked (nice article by the way). So spread your money on different platforms, try different platforms, it's a good thing, you will have the opportunity to check the platform, all its pros and cons. I find that to be the most healthy approach, to do everything by youself and to try to learn as much as you can in that process.
Its not that necessary for you to put up on various platforms 1-3 would be enough and beyond that would already be exaggerated.Its always been suggested and recommended after all the years
that never ever put your funds on an exchange for too long no matter how good and reputable it is, you cant still be sure on when it would be hacked or would become scam and other sorts.
For now there are known exchangers and even them arent excluded on the chance on getting hacked but luckyily they do able to compensate or patched up on whats been lost.