Hello Kapitan:

I will start with my opinion, it looks like you are using 1.75mm filament with the slicer set for 3mm filament.
This appears to be under extruded, on your 2nd post could not see the attachment.

Could we get some more information, What slicer are you using, the setting of your slicer what filament you are trying to 3D Print.
The measurements of your printed XYZ cube ect...