This is good for your first Low-Poly build, but the walls look like concrete the blue and red building, low-poly is usally with no textures. There is also too much windows and try replacing that with small dark bricks. Probably add like vents on top or usally what you would see on top of a building. I don’t know, these don’t feel so right. You right want to change the border of the window to black so it looks more low- poly. This is good though for a first build! Keep up the work!
Try and develop on detail to the buildings, expand the windows outwards, add curtains, extend the roof, make the roof detailed, use more of a variety of colours,etc.
They don’t look bad for first time at all!! Just need to add a bit more unique style or detail to make it look less boring and symmetrical but other than that great job!