Import items from a CSV file to a Sharepoint Online list

Looking at one of the screenshots you have provided I would suggest to tackle multiple potential issues as follows:

1) ensure proper encoding of you input
(not seen anywhere in this thread, but just to be on the save side keep it for later in mind).
What I definitely could not see in your screenshot is the property for the delimiter of your CSV data

#Get Import , convert to UTF
    $NewFile = $ImportFile.Replace(".csv","UTF.csv")
    Type $ImportFile -Encoding:String | Out-File $NewFile -Encoding UTF8
    Start-Sleep -Seconds 2

#Import the new created file
    $data = Import-Csv -path $NewFile -Delimiter "`t" # ";"
    start-sleep -Seconds 5
#delete the new created file again
    remove-item -path $NewFile

2) Within the Foreach put some additional brackets around the CSV column names:
  $item['Title'] = $($row.ColumnHeader)
Whereby if the header consists of multiple lines or white spaces you might want to define the column header beforehand:

variation 1:
(spacing)

$TitleHeading = "Nom Prenom"
[STRING]$MyTitle = $($row.$TitleHeading).trim()
$item['Title'] = $MyTitle

variation 2:
(whoever thought having multiple lines within the header is a good idea 😉 )

$TitleHeading = @"
Nom Prenom
(obligatoire)

"@
[STRING]$MyTitle = $($row.$TitleHeading).trim()
$item['Title'] = $MyTitle

<edit 1>:
, had a look at your screenshot to peek on your code just to notice after posting my reply that you have included it now within your initial posting.
</edit>

Micca0815 

Thanks, when I use your technique I have no errors! On the other hand my items in my SharePoint list coming from my CSV file are empty 😞  Why I don't have my values displayed 😧 ?

444456464 

as you make use of CSOM and SharePoint Online Management shell, I`d suggest to download the latest CSOM libraries from here:
https://www.nuget.org/packages/Microsoft.SharePointOnline.CSOM

and once downloaded load them into your current session.
The installed ones you are adding currently might not be compatible with SharePoint Online.

BTW. , you do not need to install those, they could be filed relative to the scripts´ location as well.
e.g. this is a shortened function I would use.

function get-assemblies {
   $sCSOMPath= $scriptDir       
        $sCSOMRuntimePath=$sCSOMPath +  "\Microsoft.SharePoint.Client.Runtime.dll"         
        $sCSOMClientPath=$sCSOMPath +  "\Microsoft.SharePoint.Client.dll" 
        #$sCSOMUploadPath= $sCSOMPath +" \Microsoft.SharePoint.Client.Publishing.dll"
            #Load SharePoint Online CSOM Assemblies 
            try{         
                Add-Type -Path $sCSOMClientPath     | out-null
                Add-Type -Path $sCSOMRuntimePath    | out-null
              }
            catch {
                Add-LogEntry $logFilePath  $requestNumber  $env:hostname 'error' "failed loading assemblies"
                return Get-JsonStatus 1 "required dlls for SharePoint on $env:computername not found."
                 }
}