Comparing a Row in XL and Speeding up macro

Question

I have a master file & i get daily updates in a separate file. I need to compare the two files, update the master with changes received, add new rows & highlight missing ones.

to compare the two files I use the following code to iterate the cells, with a unique id called ResourceRequestID(usually in the first two columns). These files have approximately 92 columns & upward of 500 rows (less than 10000 rows). How do i compare two rows & update the master with just the differences? Also, any suggestions to speed up (currently this takes about 5-8 mins) would be greatly appreciated.

'Find demands in master against the demand sheet
Sub FindDemandsInDemandSheet()
    Application.ScreenUpdating = False

    demandcount = 0
    Workbooks(Master).Sheets("Demands").Activate
    
    'Go to A1
    Range("A1").Select
    
    'find resource request id
    If ActiveCell.Value <> rRIDConst Then
        'TODO: Identify the column which has RRID.
    End If
    
    'count total number of rows
    Range("A1").End(xlDown).Offset(1, 0).Select
    demandcount = ActiveCell.Row - 2 'reducing 2 because the XL has a header & we are in the first blank cell in RRID column

    Range("A1").End(xlToRight).Offset(0, 1).Select
    colCount = ActiveCell.Column - 1
    
    Workbooks(demandSheet).Sheets("Demands").Activate
    Range("A1").End(xlDown).Offset(1, 0).Select
    destDemandCount = ActiveCell.Row
    Workbooks(Master).Sheets("Demands").Activate
    
    'iterate each RRid in master against pdac sheet
    For ctr = 2 To demandcount
        Range("A" + Trim(Str(ctr))).Select
        demandId = ActiveCell.Value
        Workbooks(demandSheet).Sheets("Demands").Activate
    'if found, get row in destination
        yy = "A2:A" + Trim(Str(destDemandCount))
        
        Set x = ActiveSheet.Range("A2:A" + Trim(Str(destDemandCount))).Find(demandId, , -4163)
        
            If Not x Is Nothing Then
                destrow = x.Row
    'Iterate columns in master
                For colCtr = 1 To colCount
                    Workbooks(demandSheet).Sheets("Demands").Activate
                    Range("A" + Trim(Str(destrow))).Offset(0, colCtr).Select
                    destValue = ActiveCell.Value
                    
                    Workbooks(Master).Sheets("Demands").Activate
                    Range("A" + Trim(Str(ctr))).Offset(0, colCtr).Select
                    sourceValue = ActiveCell.Value
                    
    'compare each cell &
    'if different, copy from demand sheet, highlight cell
                    If sourceValue <> destValue Then
                        ActiveCell.Value = destValue
                        ActiveCell.Interior.Color = vbYellow
                    End If
                Next colCtr
            Else
    'Demand not found in the latest demand sheet. highlight cell in Red
                Workbooks(Master).Sheets("Demands").Activate
                Range("A1").Select
                With Range("A" + Trim(Str(ctr)))
                    .Select
                    .Interior.Color = vbRed
                End With
            
            End If

    Next ctr
    
    Application.ScreenUpdating = True
    MsgBox "Demand Master validated against latest demand reports"
    
End Sub