Why isn't this give command with a display name working? [duplicate]

The command you got was a Java Edition only command. This will not be able to work because Bedrock Edition has a drastically different command format.

The issue you found in your image was one of the differences. Unlike JE, BE prohibits namespace values like minecraft: in item names. You must remove them, and also player_head is invalid, the correct ID is skull:

give @p skull

Additionally, the stuff in curly brackets {display:{Name:'…'}} is called NBT, which allows you to set specific item properties. Bedrock Edition commands do not have access to NBT, so you are unable to set custom player skulls in that edition.

In the future, please be wary whether the source that you are getting your commands from is a Java Edition source or a Bedrock Edition source. Commands for one edition will most certainly not work on the other.