What database to choose for a mobile application and how to properly organize the download of images with compression?

Question

MySQL

Good day to all. I have such a task, to create a mobile application for downloading ads similar to olx with almost the same functionality, one to one . Those will be paid ads like premium urgently, on the first page, etc. for a small neighborhood, there are about 5,000 people. It will be created both android and ios, I wanted to start with firebase, but I'm afraid there will be a lot of requests, and it supports the nesting structure very poorly (or rather, it is not very profitable to do this at rates). Considering that pictures will be loaded and there will be quite a few of them, it seems to me. I have almost no experience in developing mobile applications and backends for it. I myself develop purely in php (I make websites). I have several questions in my head.
1) Which database to choose and in which language is it more profitable to create a backend (php nodejs).
2) How to correctly create an authorization to create a standard session or by keys as a node, or is it better to fasten it ready from firebase?
3) How to properly and quickly organize the upload of images to the server. Somehow I wrote a mini demo on android, so through my mobile phone my script tried to upload an 8 mb image to the server, which was made on my phone without compression. It took me almost 5 minutes with my Internet on my phone. And I don't think anyone will wait that long.
4) If I use firebase auth, what are the disadvantages and pitfalls that await me in real use by clients. In principle, I think this is enough, since the application is still not big. But for me, these questions are important.

Answer 1

1) Which database to choose and in which language is it more profitable to create a backend (php nodejs).

Any on which it will be faster and more comfortable for you to work.
In other words, you ask the developer of a mobile application, he says that he needs GraphQL, nodejs is better sharpened in GraphQL, and you will trade like the market in favor of the best solution.
through tokens. if there is a normal website yet, then it’s definitely not firebase, it’s very uncomfortable. There are no sessions in the API.
Compress on the client and send the compressed image.
We had a problem in synchronization and writing methods on the php backend. if there is already an authorization system on the back, then there is no point in using firebase auth.