why my picture self by camera mirrorless rejected?

In addition what has been said (tripod, level, exposure), you need to try to process your images only lightly, not adding to much saturation and above all no fancy processing filters. Shoot raw and exposure brackets, so that you can later on select the well exposed, sharp and noiseless picture to work with. Besides a tripod, you may also use a wall or a box to put your camera on and shoot with the 2 second release timer instead of the remote, if a remote is not awailable. Set the camera in full manual mode. Look at your histograms to appreciate the exposure. With bracketing I often select a slightly underexposed picture and lighten the shadows a little bit. That preserves the highlights better. Sometimes it is also worth combining different exposures in Photoshop. That is more difficult with moving objects, but cleverly done it may enhance the image dynamic, without using a fancy hdr program. 

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

Hello,

Well, you need to get your camera level and use a tripod. Did you use a tripod?

Have a read of this from Adobe about how to create better photos:
https://helpx.adobe.com/stock/how-to/tips-stock-image-acceptance.html?set=stock--fundamentals--adobe-stock-contributor