Question: i have a javascript file about 6000+ lines of codes created by myself. Now it has functions for different sections of my site.. Now what i want to ask is that should i use that large file or divide it in parts for respective sections and call it in respective section.

Answer: 
I would suggest using 1 large one, as that requires only 1 http request. And with the right server setup it is only loaded once as it becomes cached.
It depends on how much the HTTP request cost is Vs. how likely a visitor is to access one of the sections with specific JS Vs. how much bandwidth is saved for the other pages.