How can I share my form and submissions with a colleague

I would like to share submissions as well

You can add your colleague as a Subuser to achieve this. You can allow him any (or both) of these permissions:

1. EDIT FORMS

2. VIEW SUBMISSIONS

Complete guide: How-to-Share-Forms-with-a-Sub-Account-User 

Your colleague needs to have his own JotForm account so if he doesn't have one yet, you can ask him to sign up for a free account here.