How can I separate myself from other users in the controller?

Question

Laravel

Please tell me how to separate myself and other users of the site (which will be enclosed in the $friend variable). In the task condition, there is me $user and there are others $friend.
I found only $user = Auth::user(); to refer to myself in Laravel. but this applies to everyone. Is there a more precise command?
I need this to run this code:

$users = User::all();
        $user = Auth::user();
        $friend = ??? (хз что тут писать)

$last_message = Chat::select(['chat'])->where('user_id', $user->id)->where('friend_id', $friend->id)->orderBy('id', 'desc')->first();

The chats table consists of the columns: user_id, friend_id, chat
My own attempts to do this did not lead to anything.