Honestly, while the changes between one version of AutoCAD and the next are often incremental, jumping more than a few versions at a time is always a significant leap. Based on your post, it sounds like your colleague is using AutoCAD 2013. As of today, the current version of AutoCAD is AutoCAD 2022. From 2013 to 2022 is a 9 version jump.
If the objective is truly to upskill to a new version, my recommendation would be to sign up for an AutoCAD class at your local community college. In addition to being quite affordable when compared to in-person training that might be offered by an Autodesk Authorized Training Center, doing so will accomplish a number of things.
First, taking a class at a community college will qualify you as a student, and therefore eligible to get a student license of AutoCAD at no cost.
Secondly, your community college professor has likely upgraded between every version since AutoCAD 2013 (and likely before that). As such, taking a community college class will grant you access to a subject matter expert who can help you navigate the many changes that have occurred over the better part of a decade.
In my experience, people who go it alone and jump 9 software releases at once tend to use the new version in the same way they used the old version. I say this not as a criticism of the individuals themselves, but instead as a recognition that many changes require a little help to know about and then learn to leverage in your own workflow. That insight is something a good instructor, like those in a community college setting, can help you with.