Help Please Newbie learning Unreal 4.23

I am using a few resources to learn Unreal4. One of these resources is the Lynda Videos which are now on LinkedIn. The problem I am having is opening the .umap files in the exercise folder, they are greyed out so I am not able to access. This set of Lynda videos was created in 2018. I have been able to open what I believe are project files and they were from a 2015 tutorial. I just bought an iMac a week ago which is the best iMac with extra ram (16 gig )
3.7GHz 6-core Intel Core i5,
Radeon Pro 580X 8 GB
I am getting a error message when I open UnReal saying that X code is missing.
I am struggling to get up to speed and being able to open the exercise files would be a huge plus.