Nap time

Hello everybody. I dont have a rigid routine with my LO. He does wake up at night for about an hour and then often for the dummy 😫 he seems to stay awake for most of the day time with 1 or 2 short cat naps. He keeps getting tired at 4pm. I try my very best to keep him awake until 7pm or close to that time as he whinges and is super cranky if he doesnt sleep. Sometimes he struggles so bad that he then falls asleep regardless for a nap at 4pm. What do you ladies do in this situation? He takes hours to put down to sleep at bedtime even if he hasnt had a nap