any advice for a begginer??

Before you decide to edit and upload an image, search the existing library for similars. For instance, your lemon image. Search for lemons. You will see thousands of perfectly exposed, well lit, sharply focused lemons in every possible configuration. Then compare to your image to determine whether yours has the quality and appeal to be saleable given the competition. You might also consider joining a photo sharing site, such as flickr, SmugMug, or 500px to help you improve your photography and editing skills. A snapshot straight out of the camera is rarely going to be accepted by Adobe stock.

Adobe Stock looks for highest visual and technical quality. See links below.

• https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
• https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html

Suggest you enroll in some photography courses to learn about depth of field, lighting, composition, color balance and of course how to correctly use your make & model camera.

All cameras are not created equally.  Some have lots of manual options giving you greater control over your shots while other point & click models have almost no options.  I won't say you can't use a phone but you will get better images with a higher quality DSLR with good lenses and sensors. 

Post production is every bit as important as pre-production set-up. Learn to use Photoshop or Lightroom to remove imperfections.

Have fun and good luck!

My advice is to realize that Adobe are looking for world class professional photographs for Adobe Stock, suitable for million dollar advertising campaigns, international magazines and more. This is NOT a suitable place to get education in photography - there are many courses and organisations that can help with that, and maybe one day you will indeed be a world class professional photographer. I can see you already have an eye for a shot (which is great because some people never get that), but I would guess - since you say you are a beginninner - you have much more technical stuff to learn, as well as how to improve a composition.

Moving to Stock Contributors forum.

The photos are all too dark. I suspect you didn't edit them. Even after lightening the shadows, further problems will probably become visible, such as noise. And have you ever wondered why someone should buy the photos? What makes them interesting?

You can find good advice here: https://helpx.adobe.com/support/stock-contributor.html