Q:

error on start nginx service on ubuntu vps

i am begginer user of vps, i have a reactJS app, and i wnat to deploy it on my ubuntu 18 vps with nginx. 
I have followed the stpes of this tutorial Deploying create-react-app with Nginx and Ubuntu
i had already check all the steps, but when i put the command 

sudo service nginx start

the system show's me, the next error message:

Job for nginx.service failed because the control process exited with error code. 
  See "systemctl status nginx.service" and "journalctl -xe" for details. 

and when i put "journalctl -xe" shows me this:
nginx, error
ngnix, error
please help me friends

A:

Look in your log file on messages before the error "Failed to startup nginx"
You will see the reason of problem. 
bind() to 0.0.0.0:80 failed (98: Address already in use)
Looks like port 80 on your vps server is already in use by some application. 
Port 80 used for HTTP services. 
So most likely you already have run Apache HTTP server, or some other. 
use this command to see what application use it
sudo netstat -tulpn | grep ":80"

If you see apache
tcp6       0      0 :::80                   :::*                    LISTEN      349/apache2  

then you can stop apache
# apache service name also can be httpd (use right command)
# sudo service httpd stop
sudo service apache stop

and run nginx
sudo service nginx start

But you should be sure that you don't use apache for another website.