If you have a unit with 32gb internal memory and still within your update period refer to this . It is a quickest method of making space but requires BMW being put on an external SD card. IMO it might complicate making a future software backup of your scan folder, if BMW is in another location) I had no problem using a 32GB Sandisk Class10 sd card

https://www.youtube.com/watch?v=_ufpKMi1OHw

This method is way more time consuming and involves doing a factory reset to clean out fragmented files and junk so you definitely have to re-download the system update  and car Apps over again. (I think this method might be what you would desire 30 days  before your updates expiration to get everything to fit back together on the internal drive, providing you likely won't be doing anymore updates afterwards, and then do a final scan folder backup to a USB thumb drive to save, if you aren't planning to update the tool any longer.

https://www.youtube.com/watch?v=SjkQB0otK58