Integrate Website with Synology NAS DSM access

General information for the website: Self employed. Need just 3 page website but integrate site access with user accounts on office NAS
Kind of development: New website from scratch
Num. of web pages/modules: 2 or 3 pages
Description of requirements/features: Hello there,

I have set up a small business and registered with a few agencies who hire me. I have created accounts on my DS213J for each agency so that we can share relevant documents.

I have a website which frankly has nothing as of now but just want to use it as a simple portal for my users to login (instead of giving them individual links), and based on permissions gain access to the File Station, photo station or my web calendar.

The DS213j NAS is accessible via a static IP through myoffice.mydomain.com
The web calendar is actually zoho calendar but they do provide the code to imbed in own website. I am however open to any good looking yet simple to use web calendar that will allow me to share my schedule with my business partners just for them to know my availability. (It is not meant to be a group calendar)

Can anybody help with this or point me in the right direction please.

Thanks
Payment methods: Paypal
Extra services needed: Installation, 3rd party integration, Security
Extra notes: