If I transfer BTC to a friend/family, they now know my wallet address, correct? Does this mean they can see all the transactions I have done from that wallet? It seems like wallet information is public except for identity, but that would be forfeited once I make a transfer, right?
Yes, when you are sending on a wallet like Bitcoin core. Electrum and other non custodial but if you do sent out on an exchange address then it cant really be traced up.
Dont know what you do mean about forfeited because balances cant really be touched nor be stolen from you as long you do hold your own private key of the said wallet.
They could know the wallet balance of yours but they do know that you are the ones been holding into?