PayPal App Problem

I let my friend use the PayPal App on my iPhone to log into his PayPal account once.

Now I get alerts for his account every time there is some activity on his account of payment in or payment out, even though I logged out of his account and have been using my own PayPal account only.

I only get alerts on my account some of the time when there is activity and most of the time I don't get my own alerts though as I should.

I have tried deleting the App and reinstalling, but my alerts still aren't right.

Has anyone had any similar experience or perhaps know how I can get my PayPal App to stop showing alerts for his PayPal account and to show alerts again for my own PayPal account as the App should?