Slow running Code

Hello all,
As I am sure you'll notice from the clunky code I am self taught and hoping that is why this is running so slowly. The code is doing exactly what I want it to but is taking a long time (~15 to 20 seconds) to run. The basic idea is that users use the filters on the source data tab to identify a set of rows they want to classify, they then use a user form to classify and it is copy and pasted on to an allocations tab.

Any ideas of how I can make this run quicker?

Thank you!!!

Sub CopyPartOfFilteredRange()
    Dim src As Worksheet
    Dim tgt As Worksheet
    Dim filterRange As Range
    Dim copyRange As Range
    Dim lastRow As Long
    Dim lastRow2 As Long
    Dim lastRow3 As Long
    Dim cell As Range
    
    Set src = ThisWorkbook.Sheets("Source_Data")
    Set tgt = ThisWorkbook.Sheets("Allocations")
           
       
    Application.ScreenUpdating = False
    
    '100% button
    If ToggleButton_100 = True Then
        TextBox_Allocation.Value = 100
        
    End If
        
    'checks
        If TextBox_Allocation.Value = "" And ToogleButton_100 = False Then
            MsgBox "You must enter an allocation amount"
            
        ElseIf TextBox_Allocation.Value > 100 Then
            MsgBox "The max allocation is 100%"
            
        ElseIf ActiveSheet.Name = "Allocations" Then
            MsgBox "Allocations relate to filtered rows on Source_Data tab ONLY"
        
        Else
    
    'removes filters from Allocations tab
    Application.Goto tgt.Range("C3")
    If (tgt.AutoFilterMode And tgt.FilterMode) Or tgt.FilterMode Then
             tgt.ShowAllData
    End If
        
    ' find the last row with data in column Source_Data Ref
    lastRow = src.Range("D" & src.Rows.Count).End(xlUp).Row
    
    ' find the last row with data in column Sheet 2 Ref
    lastRow2 = tgt.Range("C" & tgt.Rows.Count).End(xlUp).Row

    ' the range that we are auto-filtering (all columns)
    Set filterRange = src.Range("B2:M" & lastRow)

    ' the range we want to copy (only columns we want to copy)
    ' we set the range to start in row 3 to prevent copying the header
    Set copyRange = src.Range("D3:M" & lastRow)
    
    ' filter range Exclusions based on column B <> "Yes"
    Application.Goto src.Range("D3")
    filterRange.AutoFilter field:=1, Criteria1:=""
       
    ' copy the visible cells to tgt ranges last row
    copyRange.SpecialCells(xlCellTypeVisible).Copy
    tgt.Range("C" & lastRow2 + 1).PasteSpecial (xlPasteValues)
    
    'last row following of tgt sheet following posting
    lastRow3 = tgt.Range("C" & tgt.Rows.Count).End(xlUp).Row
        
    'transfer data from userform
    tgt.Range("M" & lastRow2 + 1 & ":M" & lastRow3).Value = ListBox_Group.Value
    tgt.Range("N" & lastRow2 + 1 & ":N" & lastRow3).Value = ListBox_Sub.Value
    tgt.Range("O" & lastRow2 + 1 & ":O" & lastRow3).Value = ListBox_SubSplit.Value
    tgt.Range("P" & lastRow2 + 1 & ":P" & lastRow3).Value = ListBox_Plants.Value
    tgt.Range("Q" & lastRow2 + 1 & ":Q" & lastRow3).Value = TextBox_Allocation.Value / 100
    tgt.Range("R" & lastRow2 + 1 & ":R" & lastRow3).Value = TextBox_Notes.Value
    
    Call Clear_UserForm
    
    'copy sumif formula
    tgt.Range("B3:B" & lastRow3).Formula = "=SUMIF($C:$C,C3,$Q:$Q)"
     
    'resets Exclusion flags
    For Each cell In src.Range("B3:B" & lastRow)
        If Not Application.IsNumber(cell) Then cell.ClearContents
    Next cell
     
    AllocationUserForm.Hide
    
    Application.Goto src.Range("D3")
    If (src.AutoFilterMode And src.FilterMode) Or src.FilterMode Then
        src.ShowAllData
    End If
    
    Application.ScreenUpdating = True
    
  
End If

End Sub