Bitcoin transaction traceability of outputs

in ethereum 101 lecture “utxo-vs-account-model-privacy-and-fungibility-3” on 4:47, Ivan said that if you send Bitcoin transaction to another address and to yourself in the same transaction and that it’s impossible to know which money went to which address.
Can you help me clarify the matter because up to this point I thought bitcoin transactions are completely transparent and you can see how much went to which address, am I missing something?

In the example above you can see in orange that some amount went to the origin address, what am i missing?

The user probably used a wallet that is not conforming to a standard implementation (or one just created a raw transaction manually and used the same address). A wallet should generate a new change address for the user for each new tx.
If that were the case the change address would not be the same so you wouldn’t be able to tell which part went back to the user.

I feel like there was lack of information about, maybe I’ll try to research more about it.

This is actually mentioned in the Satoshis whitepaper itself

Is it possible to have multiple public keys for each private key?
because if private key can only create single public address, that it’s traceable else if there is another mechanism that somehow mask the public key while doing transactions.

No, each public key corresponds to a single private key. You can however use a hierarchically deterministic wallet, which derives private keys from a single master private key. Most modern wallets should be HD wallets these days.

They were introduced with BIP32

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It’s more to do with the mechanics of how a utxo works and transacts compared to a model account such as ethereum. You will always see transparency in terms of amount and address shown, but are very different architecture in performance. UTXO is a safer model as money is not actually stored in a wallet, as like ethereum. Transactions are more stored at the address. I suggest checking out the bitcoin and ethereum course for a clearer understanding.