After you make changes to your unit file, you should run
systemctl daemon-reload, as outlined here.
Reload systemd manager configuration. This will rerun all generators (see systemd.generator(7)), reload all unit files, and recreate the entire dependency tree. While the daemon is being reloaded, all sockets systemd listens on behalf of user configuration will stay accessible.
You can then restart (or reload) your service as you desire with
systemctl restart your-service-name
(daemon-reload won’t reload/restart the services themselves, just makes systemd aware of the new configuration)