How to integrate Minio behind a Nginx reverse proxy and interacting with JavaScript API?

Question

for the past 2 weeks I am tring to get a minio service up and running but I can not solve this error.

I started with creating a nginx service with a modified version of minio's default configuration provided by them (https://docs.min.io/docs/setup-nginx-proxy-with-minio.html):

server {
 listen 80;
 server_name fs-theorie.de;

 # To allow special characters in headers
 ignore_invalid_headers off;
 # Allow any size file to be uploaded.
 # Set to a value such as 1000m; to restrict file size to a specific value
 client_max_body_size 0;
 # To disable buffering
 proxy_buffering off;

 location / {
   add_header 'Access-Control-Allow-Origin' '*';
   add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS','DELETE';
   proxy_set_header X-Real-IP $remote_addr;
   proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
   proxy_set_header X-Forwarded-Proto $scheme;
   proxy_set_header Host $http_host;

   proxy_connect_timeout 300;
   # Default is HTTP/1, keepalive is only enabled in HTTP/1.1
   proxy_http_version 1.1;
   proxy_set_header Connection "";
   chunked_transfer_encoding off;

   proxy_pass http://bucket:9000; # If you are using docker-compose this would be the hostname i.e. minio
   # Health Check endpoint might go here. See https://www.nginx.com/resources/wiki/modules/healthcheck/
   # /minio/health/live;
 }
}

My JavaScript is configured the following:

const Minio = require('minio');
const minioClient = new Minio.Client({
  endPoint: 'fs-theorie.de',
  port: 80,
  useSSL: false,
  accessKey: 'minioaccess',
  secretKey: 'miniossecret',
});

When hitting on the bucket with following method

const bucket = {
  fetchBuckets() {
    try {
      minioClient.listBuckets(function(err, buckets) {
        if (err) return console.log(err);
        console.log('buckets :', buckets);
      });
    } catch (error) {
      console.error(error);
    }
  },
};

Firefox tells me: Cross-source (decision): The same-source rule prohibits reading the learning resources on http://fs-theorie.de/.

Chrome tells me: GET https://fs-theorie.de net::ERR_CONNECTION_REFUSED without any further information.

I have no clue where to look next since I tried out everything I know in terms of system integration.

Thanks for your help!