macbook pro: windows are too big on external Samsung 32" monitor
I'm afraid this is a 'no fix' situation.
Your new monitor just doesn't have the capability to make things any smaller. 1920x1080 is "HD" standard television resolution (sometimes now called "1k"). At 32" it's going to be good for watching TV or working from 2 or 3m away.
32" at 2560 x 1440, called "1440p" or "2k" resolution would be better but still I'd consider a bit big for a 2k screen you work at on a desk. Personally I consider 27" to be right for 2k.
You can't make the screen display any more pixels than it has.