See: https://github.com/ONLYOFFICE/DocumentServer/issues/888

rm -rf /etc/onlyoffice/documentserver-example/  #Removes the whole unnessecary "example"
rm /etc/nginx/includes/ds-example.conf   #This will delete the link that stops nginx from starting with error like you mentioned
service nginx restart   #Should restart without problem
service supervisord restart  #As Example-Service is gone, it will re-register to only four active packets 
supervisorctl restart docservice   #Restart docservice and now you can see the green checkmark