Where can I edit the part in the message Have a nice day!
Also I like to add the site logo to the email as well..

Regards,
Tom

Hi
The email is coming from the html file.
Here is the file location in Jomsocial: ROOT/components/com_community/templates/jomsocial/layouts/email.html.php
You can edit this file to add your logo image and to edit the style of image.

The text that comes in the email message are coming from the language files
ROOT/language/en-GB/en-GB.com_community.ini
Find the text from line 930 Here : prntscr.com/ikx88

Regards