Why is the passenger door of my Volkswagen Beetle really hard and stiff to open?

The door of my Volkswagen is really hard and stiff to open from the inside and my dad has tried putting grease on it but it is still hard to open from the outside. It opens real good from the inside though. What should i do?|||FIRST YOU GOT TO "UN-LOCK" THE DOOR.


PUSH THE UN-LOCK BUTTON ON THE KEY FOB "TWICE" TO OPEN PASSENGER DOOR.


FROM INSIDE IT AUTOMATICALLY UN-LOCKS WHEN YOU PULL THE HANDLE.|||Put WD40 on all the working parts Grease don't soak into the moving parts like WD40 does.