I am having trouble running nginx webserver with Unbuntu 16.04

Following this tutorial https://www.digitalocean.com/community/tutorials/how-to-troubleshoot-common-site-issues-on-a-linux-server

Running - sudo apt-get update

I get -
Hit:1 https://repos.sonar.digitalocean.com/apt main InRelease
Ign:2 https://download.serverpilot.io/ubuntu xenial InRelease
Hit:3 https://download.serverpilot.io/ubuntu xenial Release
Reading package lists… Done

Then running - sudo apt-get install nginx

I get -
Note, selecting ‘sp-nginx’ instead of 'nginx’
sp-nginx is already the newest version (1.15.2-1).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

Then running - sudo netstat -plunt | grep nginx

I get -
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 15003/nginx

tcp6 0 0 :::80 :::* LISTEN 15003/nginx

Then - sudo service nginx start

sudo: start: command not found

Please can someone help!