The melody of If You Were The Only Girl In The World by Nat D Ayer runs 226 notes across 68 bars, 3:01 long in Ab at 120 beats per minute. The tab sits low on the neck, mostly under the fourth fret, one note at a time — no chords to barre and no strumming pattern to keep up with. A piano backing track plays the chords and bass underneath, so the line you are learning sounds like the record even at half speed.
Prefer to strum and sing it instead? If You Were The Only Girl In The World chords and lyrics.