Questions about D7 and D8

Hey,

I initially started my own Drupal Intranet site using D8, but because of a lack of some modules I needed for my site, I rolled back to using D7. While things are looking good; I am curious as to where I need to start to get my site really developed to my needs. I will explain what I am looking for and what skills I already have:

Note: I did do some searching on this site and say the development tools documentation, I read through the different IDE's to consider what I would use to push any kind of site development. With this considered, I do have experience programming but almost virtually no PHP. I can recognize its similarities from other languages and I also know how to edit the PHP configuration files, etc.

So for what I need:
Right now I am trying to build a intranet site that is secured for internal use only, but is able to talk with Smartsheet via their Smartsheet API. One of the reasons I rolled back to Drupal 7 was because there is a contributed module that allows you to provide an access token to Smartsheet and thus be able to post anything that the authorized account can see.

The only drawback is that the module can do only this. I want to be able to embed or create dashboards or pages for which users can actually see the contents of those Smartsheets. The first thing that came to mind would be I would use Javascript and Jquery to produce an HTML page that can do this, but Drupal is much different. It uses nodes and has a different structure that I am not familiar with.

The Question:
Where do I start to learn how to create my own custom pages for which I can embed tables of Smartsheet data?

I have programming experience and I have some web development experience, but I am unfamiliar with how Drupal handles custom pages, and how I can properly code in a special page. I am technically a Drupal noob and I am hosting my Drupal Intranet site via LAMP.