Hi there Gibi. Those are some nice character sketches. I don't feel qualified enough to comment on these characters, but I do have some advice to give on the perspective in the more building related sketches. Have you studied perspective any? Some great books on the subject are "Perspective Made Easy" by Ernest Norling and then "Successful Drawing" by Andrew Loomis.
The biggest problem seems to be that your objects are not properly related to a single horizon. I have done some paintovers which I have attached. I know these are sketches, but a certain sensibility to perspective improves one's art, in my opinion. Please ask if you have any questions about these paintovers.
Your sketches have a fantastic charm and character, something I ought to aim for more in my own work.