This is wrong, what you likely would have meant was:
cd /srv/homeassistant
But still, that is not even needed nor is anything you have tried. This thread should be marked as solved as your issue is not understanding what you should do. You do not “write your own” service by executing those commands. All you need to run is the hass command with the proper directory and user which is all in the service file. Further, the fact that you see that output means that:
You wrote the service file wrong
You daemonized it
It didn’t work
You changed the service file to what others and I have written
You never reloaded the changed file
You cannot just change the service file and think it changes anything. You must reload that file per the instructions above. Once you do that, your service will run.