Your Table does not have column name so i assume Table1.ColumnInDropdown is on the DropDown.
1. Assuming you the dropdown is Dropdown1 and the Textbox is Textbox1.
2. In Textbox1 default Put:
LookUp(Table2,ColumnInDropdown=Dropdown1.Selected.Value,Feedback)
or
LookUp(Table2,ColumnInDropdown=Dropdown1.Selected.ColumnInDropdown,Feedback)
3. Change the Patch to:
Patch( Table2, First( Filter( Table2, Feedback = Dropdown1.Selected.Value ) ), { Feedback: Textbox1 .Text } )
or
Patch( Table2, First( Filter( Table2, Feedback = Dropdown1.Selected.ColumnInDropdown) ), { Feedback: Textbox1 .Text } )
If you have issues show the formula on the dropdown
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