`next.js` api is resolved before promise fullfill? - promise

Question

I want to achieve something like this:
call my website url https://mywebsite/api/something
then my next.js website api will call external api
get external api data
update external api data to mongodb database one by one
then return respose it's status.
Below code is working correctly correctly. data is updating on mongodb but when I request to my api url it respond me very quickly then it updates data in database.
But I want to first update data in database and then respond me
No matter how much time its take.
Below is my code
export default async function handler(req, res) {
async function updateServer(){
return new Promise(async function(resolve, reject){
const statusArray = [];
const apiUrl = `https://example.com/api`;
const response = await fetch(apiUrl, {headers: { "Content-Type": "application/json" }});
const newsResults = await response.json();
const articles = await newsResults["articles"];
for (let i = 0; i < articles.length; i++) {
const article = articles[i];
try {
insertionData["title"] = article["title"];
insertionData["description"] = article["description"];
MongoClient.connect(mongoUri, async function (error, db) {
if (error) throw error;
const articlesCollection = db.db("database").collection("collectionname");
const customQuery = { url: article["url"] };
const customUpdate = { $set: insertionData };
const customOptions = { upsert: true };
const status = await articlesCollection.updateOne(customQuery,customUpdate,customOptions);
statusArray.push(status);
db.close();
});
} catch (error) {console.log(error);}
}
if(statusArray){
console.log("success", statusArray.length);
resolve(statusArray);
} else {
console.log("error");
reject("reject because no statusArray");
}
});
}
updateServer().then(
function(statusArray){
return res.status(200).json({ "response": "success","statusArray":statusArray }).end();
}
).catch(
function(error){
return res.status(500).json({ "response": "error", }).end();
}
);
}
How to achieve that?
Any suggestions are always welcome!