The rear sight IS adjustable for windage. You need a hammer and brass punch to adjust it.
An elevation change requires either switching sights or removing some metal with a file.
As mentioned by one poster this is set up as a combat gun. So it's not intended to shoot in the classic 6o'clock or "lollipop" hold where the whole black center area sits perched on top of the front blade. Instead it's intended that the top of the front sight be centered in the black and that the bullet hole will be half above and half below the top line of the front blade. A "centered" hold if that makes more sense. So if you're used to shooting a gun with the sights set up for the more classic bullseye style hold then you need to alter your methodology.
The gun will also be somewhat sensitive to the weight of the bullet and the charge pushing it. Fast 200 and lighter grain bullets will tend to come out of the bore sooner and hit a little lower. This effect isn't as noticeable on a semi auto as it is with a revolver due to the recoil spring and slide but I've found that it still matters. So if you're shooting lighter bullets perhaps try some classic 230gn ball ammo before going further.
With all this in mind if the gun still is shooting low with the right ammo and proper sight hold then I'd suggest a taller rear sight over a shorter front sight. That combat "bump" is already short enough. File off any more and it would all but disappear....
A taller rear sight would leave you with more useable front sight which is easier to see so you can get the front blade on target sooner in any sort of speed focused shooting. On the other hand you don't mention how low and at what distance the gun is shooting. If we're only looking at a couple of inches low at 15 then you only need to remove a file stroke or two from the front. Call it .015 to .02. And that much reduction would be entirely livable.
To aid in getting the sight filed correctly a trick you can use is to tape or hold a 1/8 thick spacer to the rear part of a flat file. To use this turn the file upside down and lay it on a table. Then remove the slide and put the rear sight on the spacer and front on the cutting teeth. Then push the slide over a short distance with the rear sight pressed to the spacer. This method uses the rear sight on the spacer as a leveling guide. And the spacer ensures that the cut on the front blade is angled so you don't see the flat when looking along the sights. Remove only a little and try the gun for a magazine or two. If needed SLIGHTLY widen the flat with another short stroke or two. Repeat the test.
When close I'd suggest living with the results for a few sessions. If it's consistently still a hair low then remove another stroke or two of metal. Go slow and sneak up on this as it's easier to remove a little than it is to put it back on.
