sick selection problem

hey everybody, I have a problem selecting objects that have a close color to the background, or objects that have parts that match the backsground color like a sea wave in front of blue sky, I tried lots of techniques like quick selection and color range and channels, but since the colors are too close i cannot seperate the object at all. does anyone have a soluton?

I uploaded a sample image where i tried to mask the sofa out of the background and faced this problem with.