Ellybett, my 8 week old DS2 does the same - awake most of the evening, but sleeps 5-7 hours from 11 or 12pm.
With DS1 I 'battled and battled' to get him into a routine. I listened to my mum, I dropped all his cluster feeds, DP and I would spend the best part of 3 hours upstairs in the evening trying to rock him to sleep. What a bloody stressful waste of time. He did eventually get the message, but I'm sure he would've done it himself anyway.
With DS2 we decided bollocks to all of the above, lets just follow his lead. With the exception of me feeding him every 3 hours or so, essentially he is fed and sleeps on demand. He sleeps lots in the day, has a nap early evening, then is awake for about 3 hours till our bedtime, where he tends to cluster feed a lot, then goes down for 5-7 hrs.
The difference is, I can see from his body language that he's tired, like DS1 was, but that he has no hope of getting self off to sleep, or staying asleep if I fed him to sleep, usually because he's either full of wind or is storing up a poo, or is just over stimulated. So I know that at some point, he will sleep properly in the evening, but I'm not pushing it. He's downstairs with us, in his pram as needed and comes upstairs at our bedtime. At some point I will start to encourage an earlier bedtime routine, but I know frm past experience that it's early days & there is plenty of time to encourage and develop a good evening bedtime.
So anyway, my point is it sounds like you're doing great, don't worry ! Just go with your LO's flow