Take it slow, and memorize each part before moving onto the next.
Practice it a lot and often.
I slow down and learn each song in detail with “Anytune Pro +”. If you have any apple devices it is a must for practicing and learning new songs.
You can find it here: https://goo.gl/5ipBdc (Affiliate Link)
You will need the actual song as well:
https://goo.gl/pmdmck (Affiliate Link)