Implementing erpnext for investment company

This investment company i’m supposed to implement erpnext needs to handle mostly debtor related issues like their payments in instalment (so for each instalment payment receipt has to be given to debtor) and with different interest rates for different loans , patently for late payments and employee bonuses for debt collection

and investors investments and their interest in time
and this company has several branches so they need to have separate views ,accounting ,users

I’m new to the erpnext so please can i know these use cases can be fulfilled with existing modules or do i need to create a new modules? if can what changes can be made to the default flow ? (can the sales module be edited?)

…seems you need a custom ad hoc app …