@rampprakash Thanks for your Answer but it is not working.
Let me try to explain in detail:
I have one Table in Dataverse (Manhours) with following columns:

Now I used one FORM for this table. When I press one submit button after filling details in this form I am creating one collection (displayed in Gallery5) too where I am storing all FORM submit entries. Please note this Submit button actually not for SUBMITFORM function.
Gallery5:

Now I want to Patch this Gallery back to my Dataverse Table using this ForAll and Patch functions.
I used Following Formula:
ForAll(Gallery5.AllItems, Patch(Manhours, Defaults(Manhours), {WOrder:glry5WO.Text, 'Lab Supervisor':LookUp(Manhours, 'Lab Supervisor'.Supervisor = glry5Sup.Text), 'Service Engineer': LookUp(Manhours, 'Service Engineer'.'Engineer Name' = glry5eng.Text), 'Date Started':glry5DS, 'Date Completed': glry5DE, 'Actual Work Hours': glry5AH.Text, Remarks: glry5Remarks.Text}))
But this formula is showing following error:

What formula shall I use?
I hope now its clear.