Can't debug this code. The Arrays are producing a Subscript out of Range error

I wrote the following code and it blocks the VBA procedure at the point where I define the Arrays and nb_Actions and nb_Cours. I tried changing Valeurs Action to Variant and others but it didn't work :/
It is a problem I have quite often.

Sub MatriceVarCov()
    Dim i As Integer, j As Integer, k As Integer
    Dim Valeurs As Integer
    Dim SomCov As Double
    Dim N As Integer
    Dim CoursActionbis As Range
    Dim nb_Cours As Integer
    Dim nb_Actions As Integer
    Dim Indice As Integer
    Dim Rendement As Double
    Dim Rendement2 As Double
    Dim Cova As Double
 

    nb_Cours = Worksheets("Actions").Cells(Rows.Count, 2).End(xlUp).Row - 1 'THIS LINE ERROR
     nb_Actions = Worksheets("Actions").Cells(1, Columns.Count).End(xlToLeft).Column - 1 'THIS LINE ERROR
    
    
    ReDim ValeursAction(1 To nb_Cours) As Double 'THIS LINE ERROR
    ReDim Esperance(1 To N) As Double 'THIS LINE ERROR
    'N = 4
            For i = 2 To N 
                Indice = Sheets("Classement").Cells((nb_Actions + 7 + (i - 2)), 7).Value
                Esperance(i) = Sheets("Analyse Statistique").Cells(Indice + 1, 2) 


            With Sheets("Ponderation Sortino")
                .Cells(4, 11 - i) = Esperance(i)
            End With

    
    For j = i To N
    
 
        SomCov = 0
    
        
        For k = 2 To nb_Cours
            ' Recuperation des rendements à partir du tableau calculé et affiché dans la sub rend
            Rendement = Sheets("Ponderation Sortino").Cells(5 + k, i)
            Rendement2 = Sheets("Ponderation Sortino").Cells(5 + k, j)
            SomCov = SomCov + (Rendement - Esperance(i)) * ((Rendement2) - (Esperance(j)))
            Cova = (1 / nb_Cours) * SomCov
        Next k
        
      
        With Sheets("Ponderation Sortino")
        .Cells(i + 5, j + 9) = Cova
        End With
    Next j

Next i
End Sub