Can I find my friend around me by appinventor's Location sensor ?
Maybe. It depends whether he sends you a Text (sms) with his location How to text your Location to a Phone and Display the Location on a Google Map or whether you build an app like this one
Social Distancing ... a CloudDB / Location Marker Tutorial which shows how close your friend is to you and shows your locations on a map. Both of you need to be logged into the app.