Calendar and contacts

Settings → Apps → Calendar → Accounts → Add Account → Other → Add CalDAV Account. Repeat under Contacts with Add CardDAV Account.

Server     totuldigital.com
Username   your full address, e.g. ana@example.com
Password   a device password, not your account password

Android needs DAVx⁵ from the Play Store or F-Droid; Android has no built-in CalDAV. Thunderbird supports CalDAV directly. Both can discover the accounts from the base address.

Base URL   https://totuldigital.com
Calendars  https://totuldigital.com/dav/calendars/<your address>/
Contacts   https://totuldigital.com/dav/addressbooks/<your address>/

A calendar you create in the browser appears on the phone, and an event created on the phone appears in the browser. It is one calendar, not a copy.