Quality problems Stockphotographs

9290:

You need to clean your sensor, as it has dust on. 

In addition, composition is very important, you should pay attention to that: 

Your car is probably too abstract for being included. 

With photo KFD9290 - exposure.

Read about taking silhouettes:

Silhouette Photography: A Comprehensive Guide

Hello,

In this photo - DSC00534:

Take note of the purple edge of the cow - this is called chromatic aberration. It is connected to the lens and light.

What is chromatic aberration? - beginner's guide | Adobe

Also, you need to make some small adjustments to the white balance and exposure.

User guide:
https://helpx.adobe.com/stock/contributor/user-guide.html
Exposure:
https://www.adobe.com/creativecloud/photography/discover/exposure-in-photography.html
White balance:
https://www.adobe.com/creativecloud/photography/discover/white-balance.html

Some photos are out of focus.
You will need to enlarge the image to 100% to check what is in focus before submitting it.
Figuring out where to focus is an eternal theme for photographers.