So after some research, my code was not correct, middlewares were missing. Here’s the good one :

var express = require(‘express’);
var app = express(); // create our app w/ express
var morgan = require('morgan’); // log requests to the console (express4)
var bodyParser = require('body-parser’); // pull information from HTML POST (express4)
var methodOverride = require('method-override’); // simulate DELETE and PUT (express4)
const mongoose = require(“mongoose”);
const dotenv = require(“dotenv”);
const mustacheExpress = require(“mustache-express”);

dotenv.config();

// configuration =================

mongoose.connect(process.env.DB_CONNECT, { useNewUrlParser: true }, () => {
console.log(“connected to DB !”);
});

app.use(express.static(“../front-end/dist/website”));

app.use(morgan('dev’)); // log every request to the console
app.use(bodyParser.urlencoded({'extended’:'true’})); // parse application/x-www-form-urlencoded
app.use(bodyParser.json()); // parse application/json
app.use(bodyParser.json({ type: 'application/vnd.api+json’ })); // parse application/vnd.api+json as json
app.use(methodOverride());

// Middleware
app.use(express.json());

// Templating
app.engine(“html”, mustacheExpress());

//import routes
const authRoute = require(“./routes/auth”);
const devisRoute = require(“./routes/devis”);
const messageRoute = require(“./routes/message”);
const actuRoute = require(“./routes/actu”);

//Routes middlewares
app.use(“/api/user”, authRoute);

app.use(“/api/sendDevis”, devisRoute);

app.use(“/api/message”, messageRoute);

app.use(“/api/actu”, actuRoute);

// listen (start app with node server.js) ======================================
app.listen(3000);