I received a rejection because of "bad quality". Can please somebody help me to know what is the problem and what I can fix?

You’re competing with over 75 million flower images. Your chances of making a sale are next to zero.

https://stock.adobe.com/search?k=flower

The signage is poorly lit with too many distracting shadows and background clutter. 

Also, Adobe Stock is a global service. Most customers don’t use English as their primary language.  You must take that into consideration when curating images for Stock submission.

Hello,

Chiefly, your main problem in these photos is your composition. Don’t underestimate the composition of a photo. In these photos, it is hard to tell what the subject is.

Also, it is important to think about the purpose of the shot. Often this is also forgotten. One can get tied up in the technicalities but forgot about the purpose of the photo. If you are trying to tell a story, what story is it?

Also, there could be problems with IP with the signage/property that the sign is located on!

Composition

IP

Both suffer from composition issues, and the first is quite underexposed in the shadows. Virtually all images required editing before submitting to Adobe Stock; there’s really no market for unedited snapshots.

in addition, the flower photo is poorly cropped and the shadows are underexposed.

The sign and the patio

There are a lot of distractions with in the image. 
Over exposed sign
Just not sure what story the image is telling.

The Flowers
People want clean images and space to add text / copy. 

Cheers

Nate