Displaying posts in homepage

Hello, I’m having a little problem on doing a thing in my app.
My app allows people to write post, which will be shown on the homepage. A post is composed of: avatar and nickname of who wrote the post, title, description and image of the post. On database, data are organized in this way:

and I want to show posts in a chronological way (according the date).
The problem is that I’m having problems on getting posts data from Firebase and displaying them. Basically, I know the procedure to get data from DB, but in this case I had to get TagList and I put them into a list. For every tag (which where nicknames) I had to get their posts, so I used a loop with the condition “Index <= Lenght of list” but it appears very complicated. Also, to display posts, I tried using a list too but I don’t know how to put data in order (nickname, title, description, image). Is there something that can be done? Thanks.
P.S. I’m putting block codes here. They may not be correct, however.