how can i turn off the high sierra server

If you don't have Server.app installed on your system in the /Applications folder, then you're probably not running macOS Server. Server.app is the front-end for configuring and managing and uninstalling and the rest of the pieces of macOS Server, though it is the front end and doesn't need to be running. Server.app is present in /Applications in every installation, however.

The base macOS system does include Apache, and add-on packages such as AMPPS and MAMP and XAMPP add their own copy of Apache.

If you're using the add-on copy of Apache from somewhere — I don't immediately see a package AAMPS available, so I'm not sure which package you're running here — then you'll have to use whatever that package expects to manage the server.

If it is AMPPS that you are running, then (toward the bottom) the AMPPS documentation describes how the AMPPS folks expect the in-built Apache to be disabled. Or invoke the AMPPS httpd server directly (as described on that same documentation page), and see what errors might be generated. Once the in-built Apache is disabled, the in-built admin tool should be available.

Edit the httpd.conf file section:

# ServerName gives the name and port that the server uses to identify itself.

# This can often be determined automatically, but we recommend you specify

# it explicitly to prevent problems during startup.

#

# If your host doesn't have a registered DNS name, enter its IP address here.

#

ServerName localhost:80

You can find this line at number 220 in the config file.

Try "sudo apachectl stop" (with options stop|start|restart), without the quotes, in Terminal.app.