How does one schedule naps?

Soo my lo is 20 weeks old this week. We've had sleep troubles now since she hit 4 months. So basically she doesnt sleep for the night until midnight now... she often naps around 4pm, for an hour max. Then shes up but gets super tired by 7-730 pm. So we try to start her night routine for bedtime at this time. Shes fed and in jammies, falling asleep by 8 pm. Great. Except...she then sleeps maybe 20 mins to an hour. And then shes up by 9. And doesnt get tired again until 11 to 1130 pm. And then shes usually sleeping for the "night" by 12 am. But often wakes by 3 or 4 for a feed. Or sometimes she will sleep until 8 am. So I'm just wondering what the hell I'm doing wrong because I'm at a loss. My friends tell me to adjust her nap schedule but I find it hard to schedule her naps when we cant force her to sleep. We just follow her sleep cues