Calendar Suitecrm and Thunderbird SYNC

The calendar on suitecrm work in only one direction with the thunderbird calendar.

How can I synchronize the calendar modifications ?

Thanks in advanc

Solutions like the Opacus thunderbird plugin will provide this functionality.

It’s necessary the Pro version or it’s enough the free version?

Thanks in advance

The free solution should cover this but you will be best contacting the vendor directly.