How can I hide my bitcoin transactions to protect anonymity from others?
Your address is a classical 1 (Pay-to-public-key-hash) address. Your friend has a newer Bech32 Pay-to-Witness-public-key-hash-type address. The block explorer you referenced is partially compatible with Bech32. Sometimes, it doesn't work. On the other hand, there's nothing that prevents you from looking at your friend's transactions using a different block explorer such as https://Blockstream.info or https://blockchair.com/.