I need help to customize my smart contract lottery project - solidity

Question

Things that I need to add as functions:
I want to integrate a management fee of 1% of the total pot. Execution: The management fee (going to contract owner) will be deducted to the total prize before the remaining 99% amount will be sent to the lottery winner. I need to add it to the selectWinner function.
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
contract Lottery{
address public manager;
//global dynamic array for participants.
address payable[] public participants;
constructor()
{
//msg.sender is a global variable used to store contract address to manager.
manager=msg.sender;
}
//receive function only creates once in a smart comtract.
//this function help to transfer the ether.
//always use with external keyword and payable.
receive() external payable{
//require is used as a if statement. it check if ether value is 2 then only run below code.
require(msg.value==0.02 ether);
participants.push(payable(msg.sender));
}
function getBalance() public view returns(uint){
//only manager check the total balance.
require(msg.sender==manager);
return address(this).balance;
}
//this random function will genrate random value and from participant array and then return to the winnerFunction.
function random() public view returns(uint)
{
return uint(keccak256(abi.encodePacked(block.difficulty, block.timestamp, participants.length)));
}
//this function decide the winner randomly.
function selectWinner() public{
require(msg.sender==manager);
require(participants.length>=3);
uint r=random(); //call random function.
uint index=r % participants.length; //for making random function value in array length range.
address payable winner;
winner=participants[index];
winner.transfer(getBalance());
participants=new address payable[](0);
}
}
I need help to do it. Thank you.

Answer 1

I think something like this should work. I don't have time to test the function right now, but will edit this answer later today. Hope it helps you at the moment.
function selectWinner() public {
require(msg.sender==manager);
require(participants.length>=3);
uint r=random(); //call random function.
uint index=r % participants.length; //for making random function value in array length range.
address payable winner;
winner=participants[index];
uint balance = getBalance(); // balance is in wei
uint fee = balance * 0.01 ether; // 1% in wei
uint amountToTransfer = balance - fee;
winner.transfer(amountToTransfer);
_withdrawFee(fee); // transfer fee to manager
participants=new address payable[](0);
}
function _withdrawFee(uint feeAmount) payable private {
msg.sender.transfer(feeAmount);
}