Firstly: Bend its neck so it's face is just down close to you.

Secondly: No need to worry about the breaths part anyhow. CPR now for one person is compressions only. The time it takes for you to do breaths and stop compressions is worse than doing no breaths at all with non stop compressions.

Thirdly: I don't imagine you could do a damn thing with cpr to get blood moving all the way up and around a giraffes brain to help.