Free up storage on iPhone

I'm trying to free up storage on my iPhone 12, 64GB. iOS 18.6.2. Couple of questions:

1) Messages has 2.1GB in Other, but clicking on this shows nothing at all. What is this 2.1GB of Other, and how do I delete it?

2) I'm storing Photos in iCloud, not downloading them. However it shows 4.45GB of documents & data in the app and I can't see what it is. How do I see what this is and delete it?

TIA

Peter