data reduction

You can use a macro similar to the following

Sub reduce_data()
    
    Dim first_cell As Range
    Dim last_row As Long
    
    
    last_row = ActiveCell.End(xlDown).Row
    
    While (ActiveCell.Row <= last_row - 5)
        ActiveCell.Offset(1, 0).Select
        For i = 1 To 5
            ActiveCell.EntireRow.Delete
            last_row = last_row - 1
        Next

    
    Wend
    
    
    
End Sub

Select any cell on first row of your data and run it. It will keep fifth row till it reaches the first empty row.