iMessage taking up 1/3 of my storage

I have my messages deleting themselves after 30 days - I deleted all my recently deleted messages - I have one group chat that is rather active, that I tried to delete, my iPhone will not allow me to delete it. Every time I do so it comes back with the full conversations and then causes my phone to freeze and I have to restart it. I no longer have storage to take photos - I have deleted 200 photos today and am unable to take 1. There has to be a solution rather than spending x amt of money buying a new one. This is ridiculous.

Update since deleting every single message I have the number of GBs for my "documents and data" has actually increased - this is insanity