Add troubleshooting section to the quickstart selfhosting (#104)

Add remove steps

src/pages/selfhosted/selfhosted-quickstart.mdx

@@ -57,4 +57,20 @@ Once the script execution is complete, you can access your netbird instance via
 
 ### Creating users
 If you want to add additional users, you can access Zitadel's management console via the URL `https://netbird.example.com/ui/console` with the same credentials. Follow the [Users guide](https://zitadel.com/docs/guides/manage/console/users)
-from Zitadel to add additional local users or integrate Zitadel with your existing identity provider by following the guide [Configure identity providers](https://zitadel.com/docs/guides/integrate/identity-providers).
+from Zitadel to add additional local users or integrate Zitadel with your existing identity provider by following the guide [Configure identity providers](https://zitadel.com/docs/guides/integrate/identity-providers).
+
+### Remove NetBird
+To remove the NetBird installation and all related data from your server, run these commands from the folder where you installed NetBird:
+```bash
+# remove all NetBird-related containers and volumes (data)
+docker compose down --volumes
+# remove downloaded and generated config files
+rm -f docker-compose.yml Caddyfile zitadel.env dashboard.env machinekey/zitadel-admin-sa.token turnserver.conf management.json
+```
+
+### Troubleshooting
+
+- I'm trying to register a user but I didn't receive a verification code. Whats is the problem?
+
+    The NetBird quickstart script generates a user name and a password for the administrator. This should be enough to login and manage your network.
+    If you want to register a new user and invite them via email, you need to configure a SMTP server in Zitadel. See [this guide](https://zitadel.com/docs/guides/manage/console/instance-settings#smtp) or details.