You can use TeamGantt's CSV feed feature to export your TeamGantt project data to a Google sheet. Changes you make in TeamGantt will be updated in your Google sheet automatically. It is a one way feed, so it is not possible to make changes in your Google sheet and have them sync back to TeamGantt.
To setup the CSV feed, first open your TeamGantt project (or projects) in Gantt chart view. Then go to Menu > CSV Feed:
Then copy the resulting link:
Next, open your empty Google sheet. In the first cell (upper left), type in: =importdata("pasteyourlinkhere") and press enter. Your TeamGantt project data in CSV format should populate the Google sheet immediately. It should look like this:
Now you're done! Your Google sheet will update the data from TeamGantt at regular intervals. Google's website currently suggests it could take up to one hour for sheets to update the data. If you would like to force a refresh, simply click the first cell with your import formula, copy it, delete that cell, and then paste your formula back into it. This will force Google sheets to pull fresh data from TeamGantt.