Add Messenger to Site

My website is in cakephp I currently have a message system on my website and I would like to delete all files and contents and create a new one. I want to add messenger to my website. Please see the attached image. When you click the gold messenger icon at the top of the screen, you will see the left column displayed on the screen in a popup. The right column will not be displayed. When you click any of the left column messages, the right column will display in a popup over the left column. The messenger at the top of the screen will display the # of unread messages in red icon. The left column, when there is an unread message, the # of messages will display in red icon. I have also attached a mobile image. I want the messenger icon to display at the bottom of the screen like you see on this image. When you click it, the messenger left column popup will appear. When a message is sent, an email will be sent to the user’s email saying they have received a message from a user and give them a link to view the message. The link will send them to [login to view URL] and then display the left column.