Hello, the OS is read only by design so you can’t install Git on the OS, but you can install it in your container. I would try the display first without any configuration if you haven’t already. I’ve found that many work out of the box with the drivers already included in the OS.
If you find that you need to add an overlay though, see this section of our docs for more details. Also, you should only modify the config.txt file before the first boot. After the device has been provisioned, you can use the configuration tab on the dashboard. (More details here)
Finally, here are some other threads with similar questions and answers: