Quality

Phone cameras are convenient & simple to use for quick snapshots.  But they're also very limited at what they can do. The picture quality will never be as good as your competition's.  Adobe doesn't care what equipment you use but the results must meet highest quality standards.

• Start saving for a new or used DSLR camera, tripod and a couple of decent lenses. 
• Enroll is some photography courses.
• Join a photography club and go on photo field trips together.
• Practice, practice, practice.

Good luck!

Unedited cellphone images are rarely going to be acceptable. Virtually every image, even those taken with a high-end DSLR camera, require at least minimal editing. If you want to be successful submitting images for stock use, shoot in RAW and learn basic editing skills.

Segundo piso Exconvento Templo de Santo Domingo de Guzmán.jpg - had it not been rejected for quality reasons, you would have needed model releases for the recognizable people in the image. 

Templo:

Before coming to the quality issues, I suppose you have uploaded a signed model release from at least those people pointed out here:

I'm sure that even a few in the crowd would need a model release.

Rule: do not publish pictures where there are a lot of (to you) unknown people. You will get a refusal for missing model releases even if the picture is submitted in an excellent quality.

The same is true also for elements with logos:

Those need to be edited out, or you need to provide a property release from the logo owner.

Now for the quality issues:

• The sun area is over exposed, the shadow area is underexposed. You need to edit your picture accordingly: lowering exposure for the over exposed areas, lifting the shadows in the under exposed areas.
• There is noise in the darker area (1) and the colours are washed out (2).

  That is typical for phone pictures in very demanding light situations.

• The shadow area is exposing a colour balance issue. You have to shift the colour balance to warmer tones. White should be white, not blueish:
• Composition:
  
  

  What is your motive? The church (1)? The art installation (2) (could also require a property release from the artist)?
  In all cases, the car (5) should not be in the picture (I know, it's getting complicated), the houses (3+4) should be straightened.
  The geometry could be corrected like this:

  

  (I have also corrected a bit the exposure)

   

For the second, you have washed out colours (1) and noise (2).

…and that not only at this place, but pretty over the whole asset.

…as shown here on the fountain. The in-camera optimization eliminated the fine details and contrasts.

This lady and the gentleman both require a model release, but you could also edit them out:

There is a similar issue on your last asset:

Water droplets should be recognized as droplets:

Noise and artefacts and washed out colours and missing details and structure where you look:

Conclusion: Your phone does not produce the pictures in the quality as needed for stock. With a small sensor camera, you need to select carefully your subjects. Otherwise, you do not meet the quality requirements. As for your motive selection, you will need to improve the composition of your images. None of the assets shown here has an excellent composition.

Hello,

Good photos for holiday snaps, but not good for stock to be honest. Composition isn't really that good for stock photos.

Then there is the quality aspect. Smartphone pics are generally not good for stock - though it does depend on the subject matter and how it is taken.

Read these materials in order to get a better idea of what Adobe wants.

User guide:
https://helpx.adobe.com/stock/contributor/user-guide.html
Exposure:
https://www.adobe.com/creativecloud/photography/discover/exposure-in-photography.html
Composition:
https://www.adobe.com/creativecloud/photography/discover/photo-composition.html
Learn and support:
https://helpx.adobe.com/support/stock-contributor.html

Quality:

https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html

Hello, I only looked at the first photo. The horizon is not level, the photo is not focused. The shadows are to dark. It needs to be croped better. Most oimportant, you need model releases for everyone that might be able to identify themselves.