Wrong project duration

Hello,
how to make Project duration bar fixed and not influenced by changing tasks dates? Now our Project dates are from 2020-01-01 till 2020-01-31, but it shows just by task date 2020-01-12 - 2020-01-16. Which parameter can fix it?

We found solution.

https://docs.dhtmlx.com/gantt/desktop__task_types.html