the private key generated at the first login

(it is a long string nsec.... )

creates a public key npub1y2zpas28hknhkl8ppuqshes237x4tg3gp3hkkdpygsqk6yhrauhs8fgtcx

it is yours.

Everyone can see your public key and log in in "read mode", with that key, only you can log in using the private key.

I hope I was clear 😔