Although the concept is good your masking is a little rough. looks like you used the eraser tool with a soft brush.plus you have left some of the background image (sky) on the bridge. maybe try useing the pentool to mask off areas..good luck

I tried it and I think the easiest way to mask it is the alpha channel (copy of blue channel), and for the areas where alpha channels don't work, use the pen tool.

i am so new at this i not sure even how to use pen ool to mask so i used background eraser

Click on the bridge layer, then on the mask. With the pen tool click the 4 corners of the square you want to cut out. Right click on your path, make a selection and then fill it with black.

Author, if you don't want to use the pen tool, the polygonal lasso tool works just fine, but play around with both and you'll get the hang of it.

Polygonal lasso is easier probalby, especially if you are just learning. You can do better edgework with it.

leaving aside things that have already been highlighted , this is a lovely image. I look forward to further works from you author especially when you develop more skills.