If you’ve got chat backup enabled, just uninstall and reinstall WhatsApp. During setup, it’ll ask if you want to restore from backup. This only works if you backed up before deleting.
iOS updates usually run background indexing for a day or two after installation, which causes overheating. Mine cooled down after 48 hours. Just keep it out of direct sunlight and avoid heavy apps meantime.
This happens during peak hours. I usually refresh the page every few minutes or try incognito mode. Sometimes switching browsers helps too. If nothing works, I wait 10–15 minutes and retry.