I just created the eth polygon because I heard that this should help me solve the problem so I am not sure about that ))
And its mean that I cant get nfts that are not selling at opensea platform right now?
which ways to make metadata not editable ?
when an NFT that was created on opensea gets transferred or bought by someone then it will be available on chain.
the problem is that in order to add an NFT on chain gas fees has to be paid, that is why lazy minting was introduced so that you can add easier NFTs in open sea interface without paying those gas fees, but the NFT is not yet on chain.
you can learn how to deploy your own smart contract on a test net network and mint some NFTs there if you want to see NFTs on your account.