Excel filter some data from other two sheets and copy back

Hi Sago,

Check the following code and see if it performs as expected:
 

Sub RunMe()
Dim mFind, cell As Range
Dim fAddress As String
Dim cVal, x, lRow As Integer

Application.ScreenUpdating = False

Sheets("Sheet3").Select
Range("E3:Q" & Range("E" & Rows.Count).End(xlUp).Row).Delete

For Each cell In Sheets("Sheet3").Range("C3:C" & Range("C2").End(xlDown).Row)
    With Application.WorksheetFunction
        cVal = .Max(.CountIf(Sheets("Sheet1").Columns("C"), cell.Value), .CountIf(Sheets("Sheet2").Columns("C"), cell.Value))
    End With
    
    If cVal = 0 Then GoTo NextCell
    
    lRow = Sheets("Sheet3").Range("E" & Rows.Count).End(xlUp).Row

    With Sheets("Sheet3")
        x = 0
        .Select
        .Range(Cells(cell.Row, "B"), Cells(cell.Row, "C")).Copy
        Do
            x = x + 1
            .Range("E" & Rows.Count).End(xlUp).Offset(1, 0).PasteSpecial
        Loop Until x = cVal
    End With
    
    x = 1
    
    Set mFind = Sheets("Sheet1").Columns("C").Find(cell.Value)
    If Not mFind Is Nothing Then
        fAddress = mFind.Address
        Do
            Sheets("Sheet1").Select
            Sheets("Sheet1").Range(Cells(mFind.Row, "D"), Cells(mFind.Row, "H")).Copy
            Sheets("Sheet3").Range("G" & lRow + x).PasteSpecial
            x = x + 1
            Set mFind = Sheets("Sheet1").Columns("C").FindNext(mFind)
        Loop While mFind.Address <> fAddress
    End If
    
    x = 1
    
    Set mFind = Sheets("Sheet2").Columns("C").Find(cell.Value)
    If Not mFind Is Nothing Then
        fAddress = mFind.Address
        Do
            Sheets("Sheet2").Select
            Sheets("Sheet2").Range(Cells(mFind.Row, "D"), Cells(mFind.Row, "H")).Copy
            Sheets("Sheet3").Range("M" & lRow + x).PasteSpecial
            x = x + 1
            Set mFind = Sheets("Sheet2").Columns("C").FindNext(mFind)
        Loop While mFind.Address <> fAddress
    End If
    
NextCell:
Next cell
Application.ScreenUpdating = True
End Sub

Best regards,
Trowa