Uploading folders to sharepoint online using powerhsell

I'm new to PowerShell and Sharepoint Online and I need to upload folders and files recursively to a document library in SharePoint.

I am able to create the top-level folder but the files are uploaded outside of it. When it comes to the sub-folder it says "Access to the path is denied"

How do I upload the files into the folder and how do I upload the rest of the folders?

This is my code so far, can anyone help me?
Thanks!

#Specify tenant admin and site URL
$User = "admin@company.net"
$SiteURL = "https://company.sharepoint.com/sites/TestSite"
$Folder = "C:\FolderStructure to upload"
$DocLibName = "Admin"


#Add references to SharePoint client assemblies and authenticate to Office 365 site - required for CSOM
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\ISAPI\Microsoft.SharePoint.Client.dll"
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\ISAPI\Microsoft.SharePoint.Client.Runtime.dll"
$Password = Read-Host -Prompt "Please enter your password" -AsSecureString

#Bind to site collection
$Context = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
$Creds = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($User,$Password)
$Context.Credentials = $Creds

#Retrieve list
$List = $Context.Web.Lists.GetByTitle($DocLibName)
$Context.Load($List)
$Context.ExecuteQuery()


Function ImportFiles()
{

    #Get name of folder
    $NewFolder = Split-Path $Folder -Leaf
    $UploadFolder = $List.RootFolder.Folders.Add($NewFolder)
    $Context.Load($UploadFolder)
    $Context.ExecuteQuery()
   
    #Loop Through Folder
    Foreach ($File in (dir $Folder))
    {
        #If file
        If($File)
        {       #Upload file to Sharepoint
            $FileStream = New-Object IO.FileStream($File.FullName,[System.IO.FileMode]::Open)
            $FileCreationInfo = New-Object Microsoft.SharePoint.Client.FileCreationInformation
            $FileCreationInfo.Overwrite = $true
            $FileCreationInfo.ContentStream = $FileStream
            $FileCreationInfo.URL = $File
            $Upload = $List.RootFolder.Files.Add($FileCreationInfo)
            $Context.Load($Upload)
            $Context.ExecuteQuery()
        }
    #else
    #foreach (folder)
    #recurse method
        Else
        {
           recurse ImportFiles
        } 
     
     

    }
}
ImportFiles

Dearbhla Bradley