Removing hard edge of the image

Thanks for all.

Maha,

It looks as if you have a Clipping Mask or other boundary that is to small to show the whole transition, in other words the artwork extends past it.

You could enlarge the boundary to fit the artwork, or scale down the artwork to fit the boundary.

Check if the Document Raster Effects Settings give enough space around the object (you may need to open the blur effect after that).

I would extend the canvas then either use the clone tool to fill in the soft edge, the eraser tool with a soft brush to remove the hard edges, or try feathering the edge. This is assuming the background is transparent (I did not download the file).

Edit: I would do the the edits above in Photoshop.