Hey Saovry,
I have helped you add the css styling into your custom module.
Actually there's an issue where TinyMCE is stripping the following code: href="javascript:void(0);" causing the popup to not work.
We are not sure why this happens.
Therefore, I have installed JCE editor, added the codes and saved the module in that editor. If you want to edit the module, you can switch to use that editor in Joomla's global configuration.