PHP coding on wordpress for our existing website - open to bidding

We would like to add more features and functionalities to our already existing website of educational online videos. like adding a blog, adding a functionality of bifurcating the payments to teachers, segregating the list of students as per the course / time of registration and other details / assigning a course to a student after receiving the payment in cash rahter than online / making few tweaks to make the site responsive / few corrections and additions in the existing dashboard / adding a functionality enabling our teachers to take classes online which we can monitor the details and many other small changes and additions in phases. Please quote your best rates.