Creating Task Manager for Client Portal Background &amp; Problem

I've taken over our company website which was created using Craft. I've never worked with Craft and I'm beginning to like it, but the higher-ups want it done ASAP and I'm struggling understanding some things.

I've been tasked to add a page for our clients (AKA Client Portal). Each one of these pages will look and feel exactly the same with the exception of three areas (Discovery, Website, Assets) where the project manager will need to add tasks. These tasks will be a brief description and will be a link to some outside page (Dropbox or something else...).

Progress

I've created a Channel and called it Client Portal which works great! I can create a portal for each client and so far so good. The problem is I need to add these sections (not sure the proper Craft term) where they can add a Discovery task, Website task, Assets task. These are unique to the client, but will be styled exactly the same, but the content (text) will be different for each task/card. I'm not sure where to start with these sections (or whatever Craft calls them).

Can someone point me in the right direction on how I would create these sections?

I've created a JSFIDDLE to give someone a visual on what I'm trying to achieve.

https://jsfiddle.net/9goqgabp/
You could create a "Matrix Block" and make 3 type of blocks in there:
Discovery task, Website task and Assets task. If you give these blocks the fields they should need they just add whatever block they need and fill it in the way they like. You can loop over these blocks so they get displayed.

They can be filled in differently for every "Client Portal"

You can find more info about matrix blocks here:
https://craftcms.com/docs/matrix-fields

The Craft CMS Documentation is really good especially if you are just starting its really helpfull as it got all the basics and even more you need to build a website with Craft.

There is also a "Craft CMS Slack" where alot of developers discuss craft and ask questions daily so you can have a more direct explanation and probably a faster response. 

https://craftcms.com/community#slack