Your question has a lot of answers my friend, but let me start by saying, you did not start simple. What you undertook is extremely complex and thoughtful and truthfully very well crafted.
The simple answer is yes, it would take someone Familiar with the instrument considerably less time to do this, but what you have to understand is they have already put in the 1000's of hours to hone the craft. I have been playing on and off for over 20 years and I still cannot do what you did. So there is that. Could I improvise a melody over it and sneak in some phrasing and harmony, sure thing I could!! What you did was craft a whole new arrangement of an existing song. Hats off to you for the endeavour and well done I say.
Keep doing it, you will find as the understanding and familiarity grow, it will take less and less time as the ""learning"" in between will no longer be a burden because you will already know.
Most of us just start with Deep Purple's Smoke on The Water, not orchestral compositions from Jerry Goldsmith