Having difficulties while deploying my project on Ubuntu server (probably nginx config or something)

Questions and Answers
3

You should keep only the first location with root path /

    location / {
        proxy_pass http://127.0.0.1:1337;
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Server $host;
        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_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_pass_request_headers on;
    }

Take a look at the documentation.
https://strapi.io/documentation/developer-docs/latest/deployment/nginx-proxy.html#nginx-proxying