The private key is just a single key and the seed phrase contains many keys.
Sorry if this sounds like nitpicking, but confusion arises when terminology is used in a loose way, also for OP.
A private key is in the end a hopefully random 256bit number with some negligible size constraints imposed by the generator point G (private keys must be smaller than G). Edit: It's maybe more the contraint by the order of the finite group used in Bitcoin's elliptic curve; I admit not being too fluent here.
I wouldn't say the seed phrase (the mnemonic recovery words) contains many keys, but rather you can derive many many keys from it by a standardized mathematical procedure (key derivation). The mnemonic recovery words encode an initial hopefully random entropy in human readable form and include a checksum to detect an error in the word sequence.
You're not wrong, but if someone doesn't know how
HD wallets work then it may be confusing to say a seed phrase "contains many keys". Or it's just me, nitpicking...
Hi, i have created my own private key, public key and seed phrase.
But i can't see the option to add a seed phrase to my private key.
When i created my wallet it asks you to set a type of address and the private key, i created a bech32 address with the private key successfully.
Why do you start with a private key? A
HD wallet usually starts with some random entropy which is represented by the mnemonic recovery words. From there you decide what kind of addresses you want to use (Electrum is fixed on one address type in one particular wallet, eg. native segwit addresses that begin with bc1q....).
When the derivation path is determined, child keys are derived and the
HD wallet takes care of that.
You may want to have a read here:
https://learnmeabitcoin.com/technical/keys/hd-wallets/In Electrum you can't add an arbitrary independant private key to a
HD wallet, you can only sweep (ie. empty) the independant private key to an address generated and controlled by that
HD wallet.
Is there a way to add my seed phrase to that private key?
I would say, no.
If i start a new wallet and use the seed phrase i have instead, can i make it bech32?
If your seed phrase (the mnemonic recovery words) is BIP-39 compatible, you can import that to Electrum and choose to have native segwit key derivation with bech32 bc1q... addresses.