Can someone figure out the private key from the address you give them to receive coins?
There’s no need to export your private key unless necessary. If you really need to back it up, don’t copy it into an online notes app.
Put simply, you can derive an address from a private key, but you can’t work out the private key from just the address, so sharing your receiving address with others isn’t dangerous.
$BTC is currently at 68833.8.