Nginx 502 proxy_pass connect() failed (111: Connection refused) while connecting to upstream

Adding common proxy_pass to another container on server and getting this error (in title). Found some issues, but it seems they doesn’t help me. :( Backend is on 8080 port netstat -plant

tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      528/systemd-resolve 
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      681/sshd: /usr/sbin 
tcp        0      0 138.68.24.18:22         112.85.42.67:55747      ESTABLISHED 108245/sshd: root [ 
tcp        0      0 138.68.24.18:22         5.19.1.53:2686          ESTABLISHED 106286/sshd: root@p 
tcp        0    340 138.68.24.18:22         5.19.1.53:2604          ESTABLISHED 108038/sshd: root@p 
tcp        0      0 138.68.24.18:22         5.19.1.53:2471          ESTABLISHED 105166/sshd: root@p 
tcp6       0      0 :::80                   :::*                    LISTEN      107898/docker-proxy 
tcp6       0      0 :::8080                 :::*                    LISTEN      93312/docker-proxy  
tcp6       0      0 :::22                   :::*                    LISTEN      681/sshd: /usr/sbin 
tcp6       0      0 :::443                  :::*                    LISTEN      107887/docker-proxy 
tcp6       0      0 :::8000                 :::*                    LISTEN      1232/docker-proxy   
tcp6       0      0 :::9000                 :::*                    LISTEN      1220/docker-proxy   

Nginx config

server {
    listen              443 ssl http2;
    listen              [::]:443 ssl http2;
    server_name         hiddendomain.com www.hiddendomain.com;
    root                /var/www/hiddendomain.com/public;

    # SSL
    ssl_certificate     /etc/nginx/ssl/hiddendomain.com.crt;
    ssl_certificate_key /etc/nginx/ssl/hiddendomain.com.key;

    # security
    include             nginxconfig.io/security.conf;

    # index.html fallback
    location / {
        try_files $uri $uri/ /index.html =400;
    }

    location /api {
        proxy_pass http://0.0.0.0:8080/;
    }

    # additional config
    include nginxconfig.io/general.conf;
}

# HTTP redirect
server {
    listen      80;
    listen      [::]:80;
    server_name .hiddendomain.com;
    return      301 https://hiddendomain.com$request_uri;
}