I will develop rest API using nodejs and express

Basically, the function and API routes that you need me to code. (Ex: An image uploading function, function for a calculation or an API for user registration/login etc.)

By this what I mean here are the users that are involved in the function/API and if we are developing a system from the scratch then all the users involved in the system. (Ex: Admin, Student, Teacher etc.)

This means the steps taken to run or the condition to trigger a certain function. (Ex: Storing student information in a cookie after he/she sign in to the system or prompting a user to select an image and then upload it and save it after pressing a button etc.)

This means what is your Database Management System (Ex: MySQL, MariaDB etc.)

This mean the name of table/tables that will be used for a specific function (Ex: for student login “Student Table” etc.)

Then I can analyze your requirements for you for a fair price or you can analyze your requirements yourself and then contact me again

Of course. Prices can be changed based on your requirements and the scope of your project

Assuming it's coded with EJS and NodeJS, YES I can modify your existing web app.

You might have to send me the pages that needs to be modified with relevant Java scripts, Stylesheet, Images and directories, Code of the existing api endpoints you want to modify and the structure of the tables related to the pages & functions you want to modify etc.