These renders are all excellent, Waleed. In the first post I like both of the images, but the night time version is a little better. I like that you have taken care to provide reflections which help further the sense of mood.
In your second post I love the moody sky and the materials and the overall presentation. Has a night time feel yet everything is visible, nice job!
In the third post, the sky is amazing. The structures look great the only thing I might reconsider is the amount of lens flaring, but otherwise it looks great.
In the fourth post, I love these towers!!!!! The sky is also amazing. I could easily imagine people really living in the structure. I love the windows and the way the floors are arranged. Perfect!!!
In the fifth post I’d say that the architecture looks great again, I like the style of the windows and the overall layout of the building.
The sixth post is another very successful model. I really like how you use cylinders to create towers.
Overall, Id say you are making good progress with your modeling and lighting. As always your vegetation looks good even though it is not Bryce vegetation. Working with Bryce 5 only I think these are fantastic renders.
All the best.