So, I was using Bitbuy to buy and send eth to the wallet of my friend. I dont know how but that transaction finish as internal and it doesnt appear on friends wallet. Does anyone know who needs to do what? very frustrated
Internal transactions are value transfers originating from smart contracts, they are not literal transactions like the ones between externally-owned-accounts and are not shown directly on the blockchain, but if done right are reflected later in the overall address balance.
It's quite common with 3rd party wallet providers to not show you Ether received from an internal transaction. But you can go to Etherscan and plug in the receiver's address and you should see the transaction under the "Internal transactions" tab.
Hope this helps.
Another easy way to track address activity (including internal transactions) for free is by checking out Alchemy Notify. Here's a link to their docs: https://blog.alchemyapi.io/blog/internal-transactions-notifications
To learn more about internal transactions in general, highly recommend you check out this blog post: https://docs.alchemyapi.io/alchemy/guides/using-webhooks#address-activity :)