If a friend sends you a money request via P2P transfer and you do not have enough funds to accept it, the app will show you a notification "Insufficient balance". Please tap "Top up" and send money to your wallet to have the required amount.
If you do not wish to respond to the request right away, you are able to dismiss it with the back button on Android or the cancel button on iOS. You can always get back to this open request by heading to the section "Requests" on the Home Screen of the app.
You can also reject this money request by choosing the option "Decline request".