Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.6.12+commit.27d51765.js&optimize=false&runs=200&gist=

contracts...MFC.sol

pragma solidity ^0.6.7;

contract MyFirstContract {
    uint256 number = 0;
    string[] names;
    mapping(string => uint) public phoneNumbers;
    
    function addPhoneNumber(string memory _name, uint _number) public {
        phoneNumbers[_name] = _number;
    }
    
    function getPhoneNumber(string memory _name) public view returns(uint) {
        return phoneNumbers[_name];
    }
    
    function addName(string memory _name) public {
        names.push(_name);
    }
    
    function getName(uint _index) public view returns(string memory) {
        return names[_index];
    }
    
    function changeNumber (uint256 _number) public {
        number = number + _number;
    }
    
    function getNumber() public view returns(uint256) {
        return number;
    }
    
    function getNumberMultiplied(uint _num) public view returns(uint) {
        return number * _num;
    }
    
    function addNumbers(uint _num1, uint _num2) public {
        number = _num1 + _num2;
    }
}