Reminder :
Don't install any app on your phone unless you have to.
Even if your friend has developed that app and he is honest, the advertisements he has bundled with his app will silently track you without the developer knowing it.
Web pages are far more anonymous than apps. Which is why you will find e-commerce sites encouraging you to use their app more than their web site.
You can create 10 fake accounts on a website and use those and the owner can't reliably figure out you are the same.
The above can't be done on your phone. You are identified by everything. Your phone number, IEME, your local storage data everything.
And apps first upload your full contact list on their servers when those are run.
Avoid using apps, other than the very few ones you really use and feel are necessary.