Try setting "Default" property of text control to:

```
If(PMApprovalDropDown.Selected.Value = "Approved", "PM Approved", PMOApprovalDropDown.Selected.Value = "Approved", "PMO Approved", ProjectSponsorApprovalDropDown.Selected.Value = "Approved", "Sponsor Approved", "")
```

In place of `PMApprovalDropDown`, `PMOApprovalDropDown` and `ProjectSponsorApprovalDropDown`, use correct names of respective dropdown controls.

**Documentation**: [If and Switch functions in Power Apps](https://docs.microsoft.com/en-us/power-platform/power-fx/reference/function-if)