I need some help about quality issues....

noise due to c ropping, focus and exposure.

Welcome to the community. Adobe does only give you a general refusal reason. This is not thought to make you a better photographer, but stock contributors are supposed to know how to take pictures. Moderation is to protect customers from bad assets. But this community is here to help.

Your exposure is not good. There is a lot of black clipping (blue) and some white clipping (red), and the histogram shows very little information in between.

In addition, you have strange artefacts on your picture:

I enlarged to make those more visible, but you can sense the problem at 100% and you see them clearly at 200%.

Very disturbing is, that on the head there is near to no detail left.

Thank you all for your reply 🙂
The background of this photo was "dark, green and dirty". The crane stood in bright morning sunlight so I've tried the lighting as it is....

Proper lighting is the key to good Stock photography.

The lighting is so inadequate that my initial reaction  was "what is it"? The range between light and shadow is just too great, washing out the details in the bright areas and suppressing them in the dark areas. 

The subject isn't well lit in this photo.  The details have been washed away in both the dark shadows and the bright highlights.  It appears part of the subject is out of focus with either motion blur or from using a depth of field that is too shallow.

Hope that helps!