I’ve deleted almost all my photos, but they’re still taking up all my space.?

You'll have to find some way to compress.

how did you delete them? if you did it in an app, you may have just removed them from the app, not the phone.

try using the File Explorer or Folder app.

if they aren't listed in Pictures or DCIM folders, try clearing the app's cache.

usually when you delete something it gets placed in the recycle can and will continue to take up space until you empty the recycle can, you should also empty your cache folder as well, are you sure you want to delete all those photos forever - you could save them in the cloud

There may be a hidden trash folder in the app you're using. If they're in a trash folder they're still using space. Use a search engine to figure out how to permanently delete photos using that app. Some apps don't allow us to permanently delete, we have to use the bloatware pre-installed Gallery app to do that. That might be what it is too if you deleted them from an app you installed instead of the photo storage app the phone came with pre-installed. 

Did you totally delete them, or did you just delete them to the garbage can where they still are taking up space ?

Have you tried a restart or switching off and on again ?