How can I return a stolen iPhone to the owner?

no not really

best you can do is to hand it in with your local law enforcements or a local lost and found.

apple do not get involved tracking their customers

szon248 wrote:

Hi! About a week ago i bought a iPhone 7 from stock market in my local area. It was sold for me in an unknown condition but for a very cheap price so buyed it. I charged it in my home and i saw iCloud lock screen.

The All Too Common SAD Reality of Buying a Used iPad/iPhone – Apple Community

I was thinking maybe i can do something good for someone and maybe i can send this iPhone back to real owner. Language in screen is not in my native language but germany so maybe thats the destination of this phone? Can someone help me with this?

Unless the owner has chosen to display contact details, the Locked to Owner screen won't show any. This is to protect the privacy of the owner.

If the seller has "disappeared" (as is all too common in these situations), turn the phone in to the police.

Ayybeeshafi wrote:

if you can see their icloud account email on the display screen, you can drop them an email about their iphone.

Nope. The email address displayed on an activation locked iPhone will be incomplete, so that's not going to be possible.

if you can see their icloud account email on the display screen, you can drop them an email about their iphone.

think also that if a thief discovers they can't use the device they don't just settle for a finders fee, or lure the owner to somewhere where they can mug them.