How to create a system with a project schedule?

Question

PHP

Hello. I have a question about a system that schedules a project for a client. I want to create and implement a similar system for my agency.
The essence of the system - When starting work with the client, he is given input data into the system, in which he can track the current state of the project and the deadlines for the implementation of current tasks on his project.
Approximate how the system works:
– For administrators: The administrator creates a client profile, then gives him input data, then a project schedule on his page.
– For clients: The client receives input data, enters the system, looks at the schedule of work on his tasks and, through a special feedback form, can make changes to the deadlines for the task and write his comment.
I want to write such a system myself, and I want to ask you where to start, what technologies to start from and ask you to describe in more detail how to implement it. If this system is already ready for implementation and there is a link with a description about it and the purchase, then attach the link to your message. I've attached a picture to this question so you can see what I'm talking about.
If anyone is ready to help in creating the system, please email me, or leave a link to your VK account in the message.
Thank you.

Answer 1

in one form or another, there are many places, for example
https://www.bitrix24.ru/features/planning.php
https://megaplan.ru/

Answer 2

Here is an overview of the most famous task accounting systems:
https://habrahabr.ru/post/276873

Answer 3

uh..... Jira not? Or have I misunderstood something?