Looking for ready made scripts/source codes


I am starting a new business, I already have a web app in development, as its taken longer than expected ( 1yr 7 months so far ) I need some ready made scripts i can integrate into the website so i can get it complete, that can be altered if i need to( it will be compatible for all devices )

These are what I need-
It is a for a multi vendor system on a two way platform

Appointment booking system
Web Video editing feature
Messaging system

I can discuss the details in more depth when the right person replies