Welcome B.olga,
Thank you for using Apple Support Communities. Based on your post, when going to Settings > [Your Name] > iCloud, the backup doesn't show up as completed, but when you select iCloud Backup here; it shows it did indeed backup. We'll do our best to assist.
Given the screenshots, which were helpful, we'd say this is an error when you look at your iCloud Settings. However, the device did backup properly, as stated in those photos.
With that said, you can choose to 'Backup Now' and set it to perform a new backup if you are worried at all: Back up your iPhone, iPad, or iPod touch to iCloud
If you complete a new backup in iCloud, does the issue persist? If so, please reply back with the following:
- Does this continue when Low Power Mode is disabled?
- Any help changing Wi-Fi networks? (Testing on another network?)
- Have you made any recent changes to your iPhone?
Hope it helps out, take care!