Saving File Space with Drupal 8 I have a hosting account which has a maximum of 250 MB total space. I have installed Drupal 8 and I'm using the bootstrap theme and already my host has warned me that I am nearing my limit for file space. This is only going to be a small site, so it really shouldn't need that much space. Is there any way I can clear up space by deleting unused files in the Drupal 8 system?

For instance, is it possible for me to disable themes and then delete those folders? And also to uninstall core modules that I'm not using and delete those folders as well? Or are there any other ways I can clear up space?

If it is not possible then I will probably switch to using Drupal 7, which would be my 2nd option.
While you could uninstall and delete core modules, I wouldn't recommend it.  They will be restored during updates and you'll have to constantly be vigilant to not go over your space limit.

Over time, the size of the site will probably grow slightly due to additional updates, and you may add files of your own (images, etc.) that also increase the site's size.

Drupal 8 requires significantly more space than Drupal 7 and is a very tight squeeze if you only have 250 MB.  Hosting recommendations are off topic for this site, but there are many hosts that offer more file space (say, 1 GB) at a reasonable rate.  If Drupal 8 otherwise fits your needs, I would pay more to increase the disk space, but if that's not an option, go with Drupal 7 since it's smaller, even with a fair number of contrib modules.