Hmm, I see where you're coming from. Let's clear this up.

So if you've got a Bitcoin wallet like BlueWallet or Electrum, that means it's already generated a pair of keys for ya - one private and one public. The public key is what you give out to people who want to send ya bitcoins.

Now, the important thing here is: as long as YOU set up the wallet and nobody else has your login info (or physical access if it's a hardware wallet), then yeah – only you have the private key. That means only you can access any bitcoins sent to your public address.

Just remember: keep that private key safe! If anyone else gets hold of it, they could swipe your bitcoins. And that'd be no bueno!