Is this a good way to structure my firebase database? - firebase

Question

I'm just starting out with Firebase (moving across from MySQL) and, after reading many documents/watching tutorials I've tried to structure the database for my "Ebay/Gumtree style app". Are there any major issues with what I've gone with?
I've sort of tried to structure it around each screen on my app so that I'm not reading a whole load of data that isn't needed (I think this is the flat structure I should be going for?), however this had led to some duplication of data (specifically images).
Is this a good way to structure the database? I've taken a few tips from here:
Best way to structure my firebase database
{
"users": {
"user1": {
"email": "example#gmail.com",
"password": "********",
"first name": "Example",
"last name": "User",
"age": "45",
"gender": "Male",
"address": "XX1 9YY"
}
},
"upload image": {
"user1": {
"image1": { #path to image
"condition": "Like New",
"price": "£100",
"upload date": "10/10/2019",
"promoted": True,
"promoted expiry": "11/11/2019"
},
"image2": {
"condition": "New",
"price": "£250",
"upload date": "12/12/2019",
"promoted": False
},
"user2": {
"image1": {
"condition": "Used",
"price": "£50",
"upload date": "05/05/2019",
"promoted": True,
"promoted expiry": "06/06/2019"
}
},
"promoted images": { #max 50 images stored here
"user1": {
"image1": #This image is a duplicated of the image above
"condition": "Like New",
"price": "£100",
"upload date": "10/10/2019",
"promoted": True,
"promoted expiry": "11/11/2019"
},
"user2": {
"image1": { #This image is also a duplicate
"condition": "Used",
"price": "£50",
"upload date": "05/05/2019",
"promoted": True,
"promoted expiry": "06/06/2019"
}
},
"categories": {
"category1": {
"image1": { #This is the third location image1 is stored
"condition": "Used",
"price": "£50",
"upload date": "05/05/2019",
"promoted": True,
"promoted expiry": "06/06/2019"
},
"image2": {
"condition": "New",
"price": "£250",
"upload date": "12/12/2019",
"promoted": False
}
},
"reviews": {
"user1": {
"review1": {
"rating": 4,
"message": "delivered on time, thanks"
},
"review2": {
"rating": 5,
"message": "great product, delivered quickly"
},
}
"user2": {
"review1": {
"rating": 1,
"message": "terrible service, took ages to arrive and was faulty!"
},
},
},
},
}
Some questions/thoughts as to why I've done things so far:
Is it a good idea to have multiple copies of the same image as it would save going through 1000s of images. For example, if I didn't have "promoted images" but wanted to find all promoted images i'd have to search through the "upload image" section (which will have many many more images than the 50 in "promoted images"
Each "category" is a new screen that will load lots of images so I've tried to separate this section out, rather than having a master "category" that gets read everytim any of the pages load.
Thanks