Clone the srsLTE repository [1], and use it to set up a demonstration system with a core network (srsEPC), base station (srsENB) and a mobile phone (srsUE). It's several hours work to set up a system that runs on a couple of Virtual Machines and bridges the IP networks together on your two VMs. You can then do pings and file transfers over your newly minted LTE network. An Intel i7 processor is fast enough to run a multi-megabit link in real time, with all three of the above components running on the same i7.
Use srsLTE's simulated channel model to start with, as if avoids the cost of hardware and the regulatory restrictions on making an actual radio transmission. Only buy radio hardware if you graduate to wanting to experiment with actual transmissions and have developed the knowledge to not get in trouble with the regulators.
Once you have the demo running, download the standards [2] and start digging though the srsLTE source code with the standards by your side for reference. The source code makes the standard digestible and includes comments with references to documents, teaching you the best places to start. Because you have a live system running you can experiment as needed to understand something.
5G is an evolution of 4G (LTE), so whilst the srsLTE isn't a complete 5G implementation it will teach you enough about 4G (which is the foundation of 5G) that you will probably be able to understand 5G.
I've found this approach to be a valuable way to learn about LTE/5G, but I do have a background in such systems. My feeling is such an approach would work for someone with a software background, even if lacking the radio knowledge, as the srsLTE source acts as a "roadmap" and the necessary background reading (MIMO, coding, ...) could be done on an as needed basis as the concept is encountered in the source code.
[1] https://github.com/srsLTE/srsLTE
[2] https://www.3gpp.org/ftp/Specs/latest