By default, Apple Watch syncs any photos that have been marked as Favourites within the Photos app on your iPhone.
Photos cannot be deleted directly from your Apple Watch.
Instead, either remove photos from the synced album on your iPhone (they will then also be removed from your Apple Watch) or - to select a different photo album (including one containing no photos, if desired) for syncing to your Apple Watch - follow the instructions here (current photos will again be removed automatically):
Siri Speaks is only available on Apple Watch Series 3 models and is not available all languages:
To check that a supported language is set for Siri on your Apple Watch, check your Siri settings on your iPhone:
On your iPhone, go to: Settings > Siri & Search > Language
Then follow the instructions here to download the Siri voice to your Apple Watch:
Note that Apple suggests leaving your Apple Watch charging overnight in order to download the Siri voice.
Check that you are following the instructions here for syncing music to your Apple Watch, including first downloading any cloud-based tracks to your iPhone for offline listening and including keeping your Apple Watch on the charger, with power connected whilst your iPhone is nearby and connected via Bluetooth (I suggest also keeping your iPhone connected to power):