It's not so complicated... 
look at this example (this one covers the SSL, which is a standard today),

https://linuxize.com/post/configure-odoo-with-nginx-as-a-reverse-proxy/

but for the localhost you do not have to use SSL.
BUT, what is the most important thing here that you are missing?
Setting up "upstream" in the header. 

upstream odoo {
 server 127.0.0.1:8069;
}

Then you use the upstream name as the name to point you proxy server.

listen 80;
server_name odoo.example.com;

location / {
     proxy_redirect off;
     proxy_pass http://odoo;  # here you pass the request to the upstream name }

But notice, I am giving to you only the essentials above, for full configuration please use the example I have provided to you or maybe even better, this one from the official deployment guide:

https://www.odoo.com/documentation/15.0/administration/install/deploy.html#id7

And remember to turn on proxy mode for Odoo, in the odoo configuration file or using the right proxy_mode=True parameter when you fire the odoo-bin from command line without configuration file.

in /etc/odoo.conf set:

proxy_mode = True

Hope this helps,
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