I'm with Pop on this, Roberto. I can understand the shot of the clocks and the shot of the typewriter. I make record shots like these often because I've learned that these things vanish. But I don't understand what you were after in the other two. For the shot of the three backs to have a chance of succeeding we'd need to see what the three are focusing on. The other shot, again mostly of backs, is diffuse. There doesn't seem to be any there there. What did you see as the focus of this shot?
But you should keep it up. You learn street photography by doing two things: (1) becoming familiar with the work of the masters of the genre, and (2) making photographs. Technically, all four of these shots are fine. What's missing is what I'd call emotional cohesion.