Hi, if i make a FIAT deposit to my Binance account from my bank account, can my bank track this? if i buy Crypto for FIAT, and make a good profit. How will they know?

In Denmark we have to pay 50% tax approx on krypto winnings (which is absurd) but i'm curious if the bank can do anything?

Tax man would not be happy with these questions. There is a way for them to know, it can be difficult though depending on how you move money, associate accounts/wallets with your identity, and cash out process.