The perspective is off all around.
The man with the backpack is walking below ground, The ships in the background are very small for as close as they are to the man on the bench, and the blue railing shows no distance perspective, they are all the same width, front to back and side to side.

Interesting concept, but somewhat sloppy execution.

PS: Straighten the horizon.

@ MossyB: OK, will try to correct and upload later. Thanks again for advice.

Interesting concept. Good luck !

work on blending colors.. the blue poles are distracting