iPhone Crashing, storage issue, 128GB help

My phone keeps crashing saying I have maxed my storage. I’ve nearly maxed my 128GB storage so I'm now backing to iCloud having bought additional storage. I am deleting photos as much as possible but it’s not always letting me delete them, sometimes it only lets me delete 3 at a time. Im also deleting large files and apps but it’s still not enough. I have no access to WhatsApp or my messages or calls in the meantime. What can I do?