problema async

// asta este functia care face submit la formularl de creare al contului

function submitForm()
{
    // check whether values are valid or not
    var xhttp = new XMLHttpRequest();
    xhttp.open("POST", "/areValuesValid");
    xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    let username = document.getElementById("username");
    let email = document.getElementById("femail");
    let params = `username=${username.value}&femail=${email.value}`;
    alert(params);
    xhttp.send(params);
    console.log(xhttp);
    var responseJSON = JSON.parse(xhttp.responseText.toString());
    console.log(responseJSON);
    if(responseJSON.msg == 'fail')
    {
        // there is a conflict ! the form must be recompleted
        if(responseJSON.err == 'usernameTaken')
        {
            alert(`username taken! please user another username than: ${username.value}`);
            window.location.reload();
        }
        else
        {
            // there is another similar email
            alert(`email taken! please user another email than: ${email.value}`);
            window.location.reload();
        }
    }
    else
    {
        // the values are valid and cand be inserted into the database
        document.forms["createForm"].submit();
    }
}

// asta este partea de cod din server, care preia xmlhttp request-ul din client si il prelucreaza, astfel incat sa determine daca datele introduse din formular sunt valide sau nu (daca mai exista dubluri in baza de date mysql)

app.post('/areValuesValid', function (req, res) {

    console.log("checking whether values are valid or not");
    console.log(req.body.username + " " + req.body.femail);

    let usernameTaken = false;
    let emailTaken = false;

    function firstQuery()
    {
        // check if username is taken
        var sql = `SELECT password FROM users WHERE username='${req.body.username}'`;
        con.query(sql, function (err, result) {
            if (!err) {
                if(result[0])
                {
                    usernameTaken = true;
                    return true;
                }
                else return false;
            }
            else throw err;
        });
    }

    function firstIf()
    {
        console.log("did the first if");
        if(usernameTaken == false)
        {
            // check if email is taken
            var sql = `SELECT password FROM users WHERE email='${req.body.femail}'`;
            con.query(sql, function (err, result) {
                if (err) throw err;
                console.log(result[0]);
                if(result[0])
                {
                    emailTaken = true;
                    console.log('email is taken');
                }
            });
        }
        return emailTaken;
    }

    var doQuery = new Promise(function(resolve, reject){
        //let decision = firstQuery();
        //console.log(decision);
        if(firstQuery())
        {
            console.log("resolved!");
            resolve();
        }
        else
        {
            console.log("rejected!");
            reject();
        }
    });

    doQuery.then(function(){
        console.log("doQuery resolved!");
        res.setHeader('Content-Type', 'application/json');
        return res.send(JSON.stringify({msg:"fail",err:"usernameTaken"}));
    }, function(){
        console.log("doQuery rejected!");
        var doFirstIf = new Promise(function(resolve, reject){
            let secondDecision = firstIf();
            if(secondDecision) resolve();
            else reject();
        });
        doFirstIf.then(function(){
            console.log("doFirstIf resolved!");
            res.setHeader('Content-Type', 'application/json');
            return res.send(JSON.stringify({msg: 'fail', err: 'emailTaken'}));
        }, function(){
            console.log("doFirstIf rejected!");
            // there are no errors, no conflicts found, success
            console.log("values are valid!");
            res.setHeader('Content-Type', 'application/json');
            return res.send(JSON.stringify({msg: 'success', err: 'null'}));
        });
    });
});