Solidity – How to Change Wei Value in Smart Contract After Deployment

I am trying to build a smart contract in solidity where the owner of the contract will deploy a contract which will have a fixed reciever's wallet address and a fixed amount of ether(20000000000000000 wei) to be transfered. An investor can transfer the required amount of ether to the reciever's wallet address. The sender can select the wallet from where the ether can be transfered to the receiver.

The owner of the contract will have the ability to change the required amount of wei in contract.

I have tried the following code in Remix IDE, the deployment works but it wont allow me to change the required amount of wei as an owner:

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

contract Wallet {
    address payable public receiver; // address of the receiver
    uint public requiredWei = 20000000000000000; // amount of wei to be sent (default value)

    constructor() {
        receiver = payable(xxxxxreceiver's wallet); // replace with receiver's address
    }

    function sendWei(address payable sender) public payable {
        require(msg.value == requiredWei, "Amount of wei sent must be equal to the required amount"); // ensure correct amount of wei is sent
        sender.transfer(msg.value); // transfer wei from sender to receiver
    }

    function setRequiredWei(uint newRequiredWei) public {
        require(msg.sender == owner(), "Only the contract owner can change the required amount of wei");
        requiredWei = newRequiredWei;
    }

    function owner() public view returns (address) {
        return address(this);
    }

    receive() external payable {
        // fallback function to receive wei
    }
}

I get the following error:
Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
Returned error: {"jsonrpc":"2.0","error":"execution reverted","id":4455215050618515}

Note: The sender's wallet has enough ether to be transfered.