Nginx – “_*” headers not seen through NGINX reverse proxy

I have setup a reverse proxy with nginx to serve my frontend over port 80, which then gets redirected to 443 ssl https and my api backend node-express on port 5000 over /api. So far the basic works except that I can't authenticate myself through json-web-token. I always get a "unauthorized".

Tried it via postman and the access_token is 100% right.

I'm sorry if this question has been asked before (have googled for a few days already) but this whole topic is very new for me and I'd rather not do something half-baked when theres security involved.

My nginx config looks like this

server {
        listen 80 default_server;
        listen [::]:80 default_server ipv6only=on;
        return 301 https://$host$request_uri;
}

# HTTPS — proxy all requests to the Node app
server {
        # Enable HTTP/2
        listen 443 ssl http2 default_server;
        listen [::]:443 ssl http2 default_server;
        server_name example.com;

        root /var/www/example.com/html;

        location / {
                auth_basic "Restricted";
                auth_basic_user_file /var/www/example.com/.htpasswd;
                try_files $uri $uri/ /index.html;
        }


        location /api {
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_pass http://127.0.0.1:5000;
        }

        # Use the Let’s Encrypt certificates
        ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

        # Include the SSL configuration from cipherli.st
        include snippets/ssl-params.conf;
}

So my questions are:

1.) What do I change here so my jwt-token get's succesfully transfered through the api backend?
2.) Do I need to explicitaly enable https on my backend server too?

Thank you!!