It can't 'repair' your battery (even if it is damaged), but it can reduce the load that the phone is putting on it - by deleting unnecessary background apps and managing screen brightness etc.
Spam for mobile phone users. You wouldn't have allowed it to run on a pc or laptop Bazile. I would do as hc advises and uninstall it, you will get bombarded and possibly be paying for the privilege.
No it's not likely there's a problem with your battery. You've been conned. Phones don't magically self-diagnose problems and then get you to install apps.