...this is the first time I've ever had Firefox struggle to upload an MSPaint .PNG
I'm really not fond of how high the turrets are - in addition to making it look like your primary goal is to capsize the ship upon launching, it just looks aesthetically awkward. I would rather make the hull (even) longer and put the superfiring turrets at least one deck lower each.
Also I can spot a few pixel errors here and there. Not great, but noticeable. I'd consider looking
here,
here and
here, but overall it's nothing really that bad.
Also I'm pretty sure the aft superstructure was just a rough placeholder heuhen had, so you might want to think about how you'd redraw that. But it looks more or less like a decent, intelligent kitbash given what it is.