Look at how msg.sender works across contracts

MeMo.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IMo{
    function callMeDifferentContract() external returns(address);
}

contract Me{
    address public senderOne;
    address public senderTwo;
    address public senderThree;


    function callMe(address moAddress) public{
        senderOne = msg.sender;
        senderTwo = callMeSameContract();
        senderThree = IMo(moAddress).callMeDifferentContract();
    }

    function callMeSameContract() public returns(address){
        return msg.sender;
    }
}

contract Mo{
    function callMeDifferentContract() public view returns(address){
        return msg.sender;
    }
}