Automatically update sheet 2 & sheet 3 from sheet 1 as per data - vba

Question

I want to automatically update sheet 2 & sheet 3 from sheet 1 as per data. It will be helpful if it gets resolved.
I am new to visual basic coding so unaware of its script but aware of c++. Whatever the solution may be it will be helpful.
Screen shot of the three sheets - I was unable to upload the Excel files
I have tried the following code:
Sub FindMatches()
Dim oldrow As Integer
Dim newrow As Integer
For oldrow = 4 To 14
For newrow = 3 To 20
If Cells(oldrow, 12) = Cells(1, newrow) And Cells(oldrow, 13) = Cells(newrow, 1) Then 'date and brand
If Cells(1, 14) = Cells(newrow, 2) Then
Cells(newrow, 3).Value = Cells(oldrow, 14).Value ' m1
End If
If Cells(1, 15) = Cells(newrow + 1, 2) Then
Cells(newrow + 1, 3).Value = Cells(oldrow, 15).Value ' m2
End If
If Cells(1, 16) = Cells(newrow + 2, 2) Then
Cells(newrow + 2, 3).Value = Cells(oldrow, 16).Value ' m3
End If
If Cells(1, 17) = Cells(newrow + 3, 2) Then
Cells(newrow + 3, 3).Value = Cells(oldrow, 17).Value ' issue
End If
If Cells(1, 18) = Cells(newrow + 4, 2) Then
Cells(newrow + 4, 3).Value = Cells(oldrow, 18).Value ' repack
End If
If Cells(1, 19) = Cells(newrow + 5, 2) Then
Cells(newrow + 5, 3).Value = Cells(oldrow, 19).Value ' extra
End If
If Cells(1, 20) = Cells(newrow + 6, 2) Then
Cells(newrow + 6, 3).Value = Cells(oldrow, 20).Value ' wastage
End If
End If
Next newrow
Next oldrow
End Sub

Answer 1

Maybe you even don't need VBA to update the data. You can simply enter a formula =C2 into a cell to reference (and retrieve the data from) a cell.
You also can reference cells from other sheets like this =Sheet1!C2.
And you can use Functions such as IF to do more complex cases and logic.

Answer 2

You just cant use Cells without sheet referencing. Because excel dont know which sheet you wana to use and assuming active sheet. So you need to you ActiveSheet.cells() and switching active sheet (but its not highly recommended). Instead use sheet declaration like this
Dim myLovelySheet as worksheet
Set mylovelySheet = Sheets("yourCuteSheetname")
and then you can work with sheet like with object (you will be familiar to it from C++)
myLovelySheet.cells()
or you can perform multiple operations on sheet with construction like this
with myLovelySheet
.cells()
.cells()
'etc
end with
Basicaly your approach is almost correct, but try study more code. I can recommend this which have multiple examples with good practise