Let say, I create wallet and have two public key and one private key.
And I remove the first public key from the wallet.
Can I restore and use my first key again? Or it's removed at all.
Sorry for the maybe a silly question I'm a newbie.
When you create a new wallet (in any recent software) a new seed is generated, from which all the private key / address pairs are generated (there cannot be an address without its specific private key); usually Bitcoin clients don't let you remove addresses from wallet, but even if you manually delete one or all of them, if you backed up your seed, you can re-generate all addresses you have used (and in the same order), since all modern wallet are hierarchical deterministic.
Here a more detailed description of how the HD wallet work: learnmeabitcoin.com/technical/hd-wallets