Let's start jamming 許冠傑 - 快樂 chords, Practice these chords sequence - C, Fm, Bb, Fm, Bb, Eb, Ab, Bb, Ab and C. I suggest starting at a calm pace of 47 BPM, and as you gain confidence, approach the song's BPM of 94. To match your vocal range and chord inclination, adjust the capo in line with the key: Eb Major.