B4J Question Append String to File does not work [SOLVED]

Public Sub WriteErrorLog(str As String)
    Try
        Dim tmpTextWriter As TextWriter
        Dim tmpWhereFrom As String
        If Main.IsServer = True Then
            tmpWhereFrom = "-Server-"
        Else
            tmpWhereFrom = "-Client-"
        End If
        DateTime.DateFormat = "dd-MM-yyyy"
        Dim LogDate As String = DateTime.Date(DateTime.Now)
        DateTime.TimeFormat = "HH:mm:ss.SSS"
        If File.Exists(Main.DirApp, "Logs/" & LogDate & "-" & Main.BrandName & tmpWhereFrom & "ErrorLog.txt") = True Then
'            If File.Size(Main.DirApp, "Logs/" & LogDate & "-" & Main.BrandName & tmpWhereFrom & "ErrorLog.txt") > 100000000 Then
'                File.Delete(Main.DirApp, "Logs/" & LogDate & "-" & Main.BrandName & tmpWhereFrom & "ErrorLog.txt")
'            End If
        End If
        tmpTextWriter.Initialize(File.OpenOutput(Main.DirApp, "Logs/" & LogDate & "-" & Main.BrandName & tmpWhereFrom & "ErrorLog.txt", True))
        tmpTextWriter.WriteLine(DateTime.Date(DateTime.Now) & " " & DateTime.Time(DateTime.Now) & " " & str)
        tmpTextWriter.Close
        DateTime.TimeFormat = "HH:mm:ss"
    Catch
        ShowLog("Error: Write Error Log", False, False, LastException.Message)
    End Try

End Sub

Dim inStr As InputStream = File.OpenInput(File.DirApp, "sample.txt")
Dim outStr As OutputStream = File.OpenOutput(File.DirApp, "test.txt", True)
File.Copy2(inStr, outStr)
outStr.Close

Sub FileAppendString(FileDir As String, FileName As String, NewString As String)
    Dim NewBytes() As Byte = NewString.GetBytes("UTF8")   

    Dim fh As OutputStream = File.OpenOutput(FileDir, FileName, True)
    fh.WriteBytes(NewBytes, 0, NewBytes.Length)
    fh.Close
End Sub

Sub FileAppendLine(FileDir As String, FileName As String, NewLine As String)
    FileAppendString(FileDir, FileName, NewLine & CRLF)
End Sub

Public Sub Schreibpreis(str As String)
    Try
        Dim tmpTextWriter As TextWriter
        DateTime.DateFormat = "dd.MM.yyyy"
        DateTime.TimeFormat = "HH:mm:ss"
        If File.Exists(File.DirApp, "test.txt") = True Then
        End If
        tmpTextWriter.Initialize(File.OpenOutput(File.DirApp, "test.txt", True))
        tmpTextWriter.WriteLine(DateTime.Date(DateTime.Now) & " " & DateTime.Time(DateTime.Now) & " " & myString)
        tmpTextWriter.Close
    Catch
        Log("Error: Write Error Log " & LastException.Message)
    End Try

End Sub

Sub WriteTextOutput (Dir As String, FileName As String, Contents As String)
    Dim Out As OutputStream = File.OpenOutput(Dir, FileName, True)
    Dim b() As Byte = (CRLF & Contents).GetBytes("UTF8")
    Out.WriteBytes(b, 0, b.Length)
    Out.Close
End Sub

DateTime.DateFormat = "dd.MM.yyyy HH:mm:ss"
Dim myString As String = DateTime.Date(DateTime.Now) & " - " & "Some log data"
WriteTextOutput(File.DirApp, "test.txt", myString)