Hi Sonika,
Ok I have some that are easily double that size on all fronts, so you don't really need to split it up yet. However if you do want to split, as a first step you might consider starting by using the expression type that lets you call another BRF+ function. That would let you start to split your main function into sub functions if you wish. You might also want to consider using Catalogs to help focus business experts and others on the most important decision tables and functions, if you aren't already using catalogs.
Regards,
Jocelyn