Nobody can, but if you had to pick an exchange then Coinbase would probably be one of the safest.

Luckily you don’t have to pick an exchange, you are free to custody your own funds (which is the whole reason crypto exists). So if you don’t want to take any chances on the solvency of a centralized entity just get yourself a Trezor and self custody.

Don’t buy with a card, that usually has high fees. Instead you could for example deposit some USDT and then make the automatic purchases using your USDT balance. You can even hold the USDT in Binance Earn while it waits to be deployed, it will be automatically drawn from your earn wallet when needed.

It depends on a lot of factors obviously, but in general I have found that fine tuning is best used to make the model respond in specific ways using the information it already possessed before the fine tuning, while context is best used to add knowledge that the model doesn’t have.