Background Changing Glitch

When we change the background of a photo, it some how blends the face features like nose, hairs, eyes with the background a little bit.

for example, I gave a picture or may be even a clear picture, while adding background it some how mess up.

Its background remover function cannot work perfectly as adobe background remover from a separate link does.

It has some limitations like using actual things from pictures, it only creates by taking parts of pictures. Good at using things related to the nature.