PROBLEMS WITH QUALITY

Beginner or expert doesn't matter.  All assets are reviewed by the same criteria.

Stock customers expect highest visual and technical quality images for commercial use.  That's what they pay for.  If you can't give customers what they expect, Stock won't accept your work into inventory.  Adobe have a reputation to protect.

Read the Stock Contributor's User Guide.   Most of what you need can be found there.

Post one or two of the full sized images and their rejection reason here for feedback.  Preview thumbnails don't tell us much.  Based on what little I can see, you have problems with light exposure and focus. 

• https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
• https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html
• https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/photography-illustrations.ug.html
• https://helpx.adobe.com/stock/how-to/tips-stock-image-acceptance.html

Sales tip.  Don't submit photos of subjects that Stock already has too much of like flowers & sunsets.  Stock has over 29 million perfect flowers and almost as many sunsets. They don't need more. Even if it's accepted, it's unlikely to sell.  Find other subjects to photograph.

Hope that helps.

"good for a beginner" is not what Adobe are looking for.  They want world class commercial photography for their discerning and demanding customers.

These appear to be thumbnails, and such small copies won't be able to be properly examined.  To get the best advice, upload the same files that you sent to Adobe.  Cheers!