You also need to modify your vote function. At the third part (end) of the function you set activefield of theProposalstruct to false. Under that line you will also reset the that are voted:

if ((proposal.total_vote_to_end - total_vote == 1) && (choice == 1 || choice == 2 || choice == 0)) {
    proposal.is_active = false;
    voted_addresses = [owner];
}

Also before the if-else statements you will add the address to the array:

voted_addresses.push(msg.sender);

So, your vote function becomes:

function vote(uint8 choice) external active newVoter(msg.sender){
    Proposal storage proposal = proposal_history[counter];
    uint256 total_vote = proposal.approve + proposal.reject + proposal.pass;

    voted_addresses.push(msg.sender);

    if (choice == 1) {
        proposal.approve += 1;
        proposal.current_state = calculateCurrentState();
    } else if (choice == 2) {
        proposal.reject += 1;
        proposal.current_state = calculateCurrentState();
    } else if (choice == 0) {
        proposal.pass += 1;
        proposal.current_state = calculateCurrentState();
    }

    if ((proposal.total_vote_to_end - total_vote == 1) && (choice == 1 || choice == 2 || choice == 0)) {
        proposal.is_active = false;
        voted_addresses = [owner];
    }
}

Notice that, in the function definition, you also added the modifiers active and newVoter. You have not created the newVotermodifier, so let's create that one too.

modifier newVoter(address _address) {
    require(!isVoted(_address), "Address has already voted");
    _;
}

You may have noticed that we have used the functionisVoted(). Do not worry if it looks unfamiliar, since you have not implement this function yet, but you will be in the future lessons. For now, just know that this function checks if the given address has voted or not.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;


contract ProposalContract {
    // ****************** Data ***********************

    //Owner
    address owner;

    uint256 private counter;

    struct Proposal {
        string description; // Description of the proposal
        uint256 approve; // Number of approve votes
        uint256 reject; // Number of reject votes
        uint256 pass; // Number of pass votes
        uint256 total_vote_to_end; // When the total votes in the proposal reaches this limit, proposal ends
        bool current_state; // This shows the current state of the proposal, meaning whether if passes of fails
        bool is_active; // This shows if others can vote to our contract
    }

    mapping(uint256 => Proposal) proposal_history; // Recordings of previous proposals

    address[] private voted_addresses; 

    //constructor
    constructor() {
        owner = msg.sender;
        voted_addresses.push(msg.sender);
    }

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    modifier active() {
        require(proposal_history[counter].is_active == true);
        _;
    }

    modifier newVoter(address _address) {
        require(!isVoted(_address), "Address has already voted");
        _;
    }


//     // ****************** Execute Functions ***********************


    function setOwner(address new_owner) external onlyOwner {
        owner = new_owner;
    }

    function create(string calldata _description, uint256 _total_vote_to_end) external onlyOwner {
        counter += 1;
        proposal_history[counter] = Proposal(_description, 0, 0, 0, _total_vote_to_end, false, true);
    }
    

    function vote(uint8 choice) external active newVoter(msg.sender){
        Proposal storage proposal = proposal_history[counter];
        uint256 total_vote = proposal.approve + proposal.reject + proposal.pass;

        voted_addresses.push(msg.sender);

        if (choice == 1) {
            proposal.approve += 1;
            proposal.current_state = calculateCurrentState();
        } else if (choice == 2) {
            proposal.reject += 1;
            proposal.current_state = calculateCurrentState();
        } else if (choice == 0) {
            proposal.pass += 1;
            proposal.current_state = calculateCurrentState();
        }

        if ((proposal.total_vote_to_end - total_vote == 1) && (choice == 1 || choice == 2 || choice == 0)) {
            proposal.is_active = false;
            voted_addresses = [owner];
        }
    }
}

In the next section you will be implementing thecalculateCurrentStatefunction to help you to retrieve the state of the current proposal.