Why the [Profanity removed] Photoshop required whole computer memory to load?

Go to the Apple menu and choose About This Mac, then click on the Storage tab.

What does it indicate for your Macintosh HD?  For example, mine reads "612.93 GB available of 2 TB".

You'll want at least 10% free just for your MacBook Pro to work well.  As far as how much you want free while you're working on your documents in Photoshop, that varies depending on the type of documents that you're working with.  

It sounds like you need to either free up space on your Macintosh HD or add fast, external storage - mabye both.

This support document gets into more details: Set up scratch disks

This document is likely to be helpful as well: Optimize Photoshop performance

Hopefully, you can get your MacBook Pro configured well soon.  It's a great laptop for creating content in Photoshop.

@Anazcmk scratch disk is not memory - how much available HD space do you have?

Please read this (in particular the section titled "Supply pertinent information for more timely and effective answers”):
https://community.adobe.com/t5/using-the-community/community-how-to-guide-tips-amp-best-practices/td-p/11601738?page=1

Edit: You had omitted to mention what Photoshop’s Scratch Disk Preferences settings are and how much free space there is on those volumes. 

Please keep your language in accordance with the forum guidelines.

Scratch disk is full means just that. The drive which you set in preferences for temporary storage of data whilst manipulating images does not have sufficient free space. I would recommend using a drive with at least 100GB free, more if you regularly work with large files.

Dave

https://helpx.adobe.com/photoshop/kb/troubleshoot-scratch-disk-is-full.html