Hi yayo,
Based off of the information you've provided here, it doesn't sound like the deployment was successful despite being able to access the web interface. You can check the status of the deployment from node01 by running 'hosted-engine --check-deployed'. You can also check the status of the VM by running 'hosted-engine --vm-status'. Could you run those commands and provide the output? It would also be helpful if you could provide the log indicated at the end of the deploy script.
As far as the storage issue, you must have an active host in order to add a storage/data domain. Typically, the first data domain added will become the master data domain, which will be indicated in the web interface by '(Master)' following the type in the Domain Type column in the Storage main tab. The host that was selected during the domain setup will become the Storage Pool Manager (SPM) and will have 'SPM' in the SPM column in the Hosts main tab. If you attempt to move this host to maintenance mode, another host will be selected to become the SPM. If no other hosts are available, I believe you'll get an error message which will prevent you from being able to move it to maintenance. I believe in this situation you can put the storage domain into maintenance mode by going to the Storage sub tab under the Data Center main tab, selecting the domain, and clicking the 'Maintenance' button. This should allow you to then put the last host into maintenance mode.
However, I think your initial deployment needs to be fixed before adding more hosts. Hopefully, I or someone else will be able to help you with that once you've responded with the output from the status commands and the setup log.