Keep on getting a 'TypeError response.json is not a function' Error

[robust frigate]

When i try to communicate with my server through the front end so that it send a request to the api i get the error stated in the title. I've tried many things but nothing works.

const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors');
const path = require('path');

const app = express();
const port = 5000;

app.use(bodyParser.json());
app.use(cors());
app.use(express.static('public'));
process.env.NODE_ENV = 'production';

const { Configuration, OpenAIApi } = require("openai");

const configuration = new Configuration({
  apiKey: 'my api key',
});
const openai = new OpenAIApi(configuration);

app.post('/completions', async (req, res) => {
    
try {
    const { prompt } = req.body;
    const response = await openai.createCompletion({
      model: "text-davinci-003",
      prompt: "Say this is a test.",
      max_tokens: 150,
      top_p: 1,
      frequency_penalty: 0,
      presence_penalty: 0.6,
      stop: [" Human:", " AI:"],
    });
    const data = await response.json();
    response.json({ completion: data.choices[0].text });
  } 

catch (error) {
        console.log(error);
        res.status(500).json({ error: error.message });
}
});
app.listen(port, () => {
  console.log(`Server listening at http://localhost:${port}`);
});
app.post('/completions', (req, res) => {
    console.log('Received request to /completions');
    // ...
  });

This is my server.js file

And this is my app.js file

import React, { useState } from 'react';
import axios from 'axios';

const App = () => {
  const [prompt, setPrompt] = useState('');
  const [completion, setCompletion] = useState('');

  const handleSubmit = async (event) => {
    event.preventDefault();
    const response = await axios.post('/completions', { prompt });
    setCompletion(response.data.completion);
  };


  return (
    <div>
      <form onSubmit={handleSubmit}>
        <label htmlFor="prompt">Prompt:</label>
        <input
          type="text"
          id="prompt"
          value={prompt}
          onChange={(event) => setPrompt(event.target.value)}
        />
        <button type="submit">Generate completion</button>
      </form> 
      </div>);}

export default App;