A simple contract that (1) deposits fund into a contract. (2) Keeps track of funds transferred into the contract.

MyContract.sol

// SPDX-License-Identifier: MIT;
pragma solidity ^0.8.0;


contract MyContract {
    address owner;
    uint256 totalFunds;
    mapping(address => uint256) balances;
    
    constructor() public {
        owner = msg.sender;
        totalFunds = 0;
    }
    
    function deposit(uint256 amount) public {
        totalFunds += amount;
        balances[msg.sender] += amount;
    }
    
    function getBalance(address _address) public view returns (uint256) {
        return balances[_address];
    }
}