nginx ubuntu user password - nginx

Question

I have a nodejs backend hosted on AWS EC2 Ubuntu 20.04 instances.
When i ssh into my server, everything is working accordingly. Today i tried configuring nginx, so i created website.com files inside sites-available .
website.com
server {
listen 80;
listen [::]:80;
root /home/ubuntu/apps/yelp-app/client/build;
# Add index.php to the list if you are using PHP
index index.html index.htm index.nginx-debian.html;
server_name api.website.com www.api.website.com;
location / {
try_files $uri /index.html;
}
location /api {
proxy_pass http://localhost:3001;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
After saving that file, i ran the following command:
sudo ln -s /etc/nginx/sites-available/website.com /etc/nginx/sites-enabled/
From the docs, in order to enable the new site i need to restart nginx using the following:
systemctl restart nginx
Unfortunately, it keeps asking for the ubuntu user password which i did not ever set.
Can someone help me out?
When i run journalctl -xe -u nginx this is what i get:
-- Subject: A start job for unit nginx.service has begun execution
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- A start job for unit nginx.service has begun execution.
--
-- The job identifier is 23231.
Jan 11 12:44:45 ip-172-31-40-105 nginx[164236]: nginx: [emerg] a duplicate default server for 0.0.0.0:80 in >
Jan 11 12:44:45 ip-172-31-40-105 nginx[164236]: nginx: configuration file /etc/nginx/nginx.conf test failed
Jan 11 12:44:45 ip-172-31-40-105 systemd[1]: nginx.service: Control process exited, code=exited, status=1/FA>
-- Subject: Unit process exited
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- An ExecStartPre= process belonging to unit nginx.service has exited.
--
-- The process' exit code is 'exited' and its exit status is 1.
Jan 11 12:44:45 ip-172-31-40-105 systemd[1]: nginx.service: Failed with result 'exit-code'.
-- Subject: Unit failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- The unit nginx.service has entered the 'failed' state with result 'exit-code'.
Jan 11 12:44:45 ip-172-31-40-105 systemd[1]: Failed to start A high performance web server and a reverse pro>
-- Subject: A start job for unit nginx.service has failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- A start job for unit nginx.service has finished with a failure.
--
-- The job identifier is 23231 and the job result is failed.

Answer 1

First be root then restart it.
sudo su
systemctl restart nginx

Answer 2

This solution provided by Mehmet works but if you require not to change user use the following:
sudo service nginx restart