vb.net form load and render speed too slow - vb.net

Question

I have a mdi parent form which, when clicking a specific button on the screen, opens a new child form. When this form loads, it needs to call the database to retrieve information, the problem is that the form takes a lot of time to load, like 15 seconds, there's not too much code in the load sub, also, I tried to remove the database code from the load event, and, although it did make it a little faster, it still takes some time to load, is there a way to fix this?
This is my form
This is my code
Public Class Deposito
Dim FormPadre As MDICajero = New MDICajero
Private monedas As ArrayList = New ArrayList
Private Sub Deposito_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.WindowState = FormWindowState.Maximized
FormPadre = Me.MdiParent
End Sub
Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
Dim ProximoForm As MenuPrincipal = New MenuPrincipal
FormPadre.LimpiarForm()
ProximoForm.MdiParent = FormPadre
ProximoForm.WindowState = FormWindowState.Maximized
ProximoForm.Show()
ProximoForm.CargaMenu(1)
End Sub
Private Sub BDepositar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BDepositar.Click
Dim dato As Emovimientos = New Emovimientos
dato.monto = montodeposito.Text
dato.idcuenta = nrocuenta.Text
dato.fecha = fechacobro.Value
End Sub End class
I've worked with java before and never seen so much load time between forms, even when retrieving information off a database.
EDIT: added a few lines to the constructor to make the form load faster, however, the rendering process it's still buggy.
Sub New()
Me.SetStyle(ControlStyles.DoubleBuffer Or ControlStyles.AllPaintingInWmPaint, True)
Me.SetStyle(ControlStyles.UserPaint, True)
InitializeComponent()
End Sub
EDIT 2: on the MDI parent form i used the same code that is automatically written when adding a mdi form to your solution, the only thing i added was an event for when the buttons are pressed to open the child forms:
Private Sub BRetiro_Click(sender As System.Object, e As System.EventArgs) Handles BRetiro.Click
Dim ProximoForm As Retiro = New Retiro
Me.LimpiarForm()
ProximoForm.MdiParent = Me
ProximoForm.WindowState = FormWindowState.Maximized
ProximoForm.Show()
End Sub
This is the code of the "LimpiarForm" function:
Public Sub LimpiarForm()
'borro todos los form hijos para no ocupar memoria, debe ser lo primero que tengo que hacer
Dim num As Integer
For num = 0 To Me.MdiChildren.Count - 1
Dim a = Me.MdiChildren(num)
a.Dispose()
Next
End Sub