i suppose that if the pup directs to one of the doorways indicates that he/she is very clean and wants/attempts to go out...at that age though, is very difficult for the puppy to control bowels/bladder...so, in my opinion you should only increase the time of taking him/her out and work up the time from there....growing will take care of the rest...

some very basic rules are that the pup need the loo when it wakes up, after drinking, after a bout of play, and before/after eating...but then, observing carefully you'll be able to understand the pup's natural routines and learn how to control them and adapt to your lifestyle!
good luck
d