Nginx setup on linux server

So I am trying to configure fully my Nginx server on my linux server.

so I did most of the work, but I had this problem where post request to php file stoped working after enforcing Nginx.

I was trying to also deploy my react apps which I was successfully despite some weird behavior, because I am newby on Nginx

so I need someone with very good Nginx experience (NO NEWBY PLEASE)

I am a stack developer but I need some one to review the code along with me and explain for my mistake and I need to fix it together, as this is a production server.

so I need some one to read my current Nginx setup, explain what is does, and then fix my mistake