My photos were rejected, can someone explain me why is this happening?

I addition to what has been said: do not submit a bunch of pictures that are very similar (that's a different refusal, but still it's a refusal).

If you are new to stock, you should consider these resources: https://helpx.adobe.com/stock/contributor/tutorials.html
Please read the contributor user manual for more information on Adobe stock contributions: https://helpx.adobe.com/stock/contributor/user-guide.html
See here for rejection reasons: https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
and especially quality and technical issues: https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html

Hi @Jan5CC1 ,

I like the framing of your images. They are however a little under exposed and too cool. To shoot in light source as you did some of these, you'll find that utilizing fill lighting helps. Please note however, depending on the distance of your subject will determine the outcome. 

Best wishes

JG