This is a great song for piano beginners to learn, as the chords used in the song are very simple and the rhythms are not too fast or complex.
Notice that the verse and chorus sections are identical, and are also the simplest chord progressions in the song.
The pre-verse section features some chords with alternate bass notes, which are the chords with a slash (‘/’) followed by another letter. The letter following the slash is the intended alternate bass note, which means your left hand will be playing a different note than the root of the chord being played. For example, Bb/C means your right hand will be playing a Bb triad and your left hand will be playing a single C note.
When you see an ‘m’ in a chord name, this indicates minor in most contexts.