Backup iPhone 12pro max by data

Hi elhadji81,

Thanks for using Apple Support Communities. Wi-Fi is necessary to backup your device to iCloud. Use the steps to complete a backup here:

1. Connect your device to a Wi-Fi network.
2. Go to Settings > [your name], and tap iCloud.
3. 
4. Tap iCloud Backup.
5. Tap Back Up Now. Stay connected to your Wi-Fi network until the process ends. Under Back Up Now, you'll see the date and time of your last backup. If you get an alert that you don't have enough iCloud storage space to complete the backup, follow the onscreen steps to buy more storage.
6. 

See more here: How to back up your iPhone, iPad, and iPod touch with iCloud - Apple Support

Thanks