*ngFor nested does not show results

I have an object that I retrieve from Firebase that has a series of properties and one of them is an array. When I try to display the properties of the object using *ngFor and I have to display the array I use another *ngFor which is nested and loops through the values ​​of this array.

When I look at the result I see the value of the properties except those in the array, but what seems strange to me is that they do appear on the console but are commented out by Angular:

<div _ngcontent-c1="" id="langOutput">
  <!--bindings={ "ng-reflect-ng-for-of": "Ada,R,D,EQ" }-->
</div>

Component used (The result of the console.log()are in the final image)

import { Component, OnInit } from '@angular/core';
import { ProjectService } from '../services/project.service';

@Component({
  selector: 'app-projectdetails',
  templateUrl: './projectdetails.component.html',
  styleUrls: ['./projectdetails.component.scss']
})
export class ProjectdetailsComponent implements OnInit {

projects: any[] = [];
languajes: any[] = [];
constructor(private projectService: ProjectService) { }

ngOnInit() {
  this.projectService.getProject().subscribe(projects => {
    // tslint:disable-next-line:forin
    for ( const id$ in projects) {
      const p = projects[id$];
      p.id$ = id$;
      this.projects.push(projects[id$]);
    }
  });
  this.languajes = this.projects;
  console.log(typeof this.projects); // 1r output
  console.log(this.languajes); // 2º output
}
}

Service to get the data from Firebase

import { Injectable } from '@angular/core';
import { Headers, Http, Response } from '@angular/http';
import 'rxjs/Rx';

@Injectable()
export class ProjectService {

  projectsUrl = 'https://proyecto.firebaseio.com/projects.json';


  constructor(private http: Http) { }

  postProject(project: any) {
    const newProject = JSON.stringify(project);
    const headers = new Headers({
      'Content-type' : 'application/json'
    });

    return this.http.post(this.projectsUrl, newProject, {headers}).map(res => {
      console.log(res.json());
      return res.json();
    });
  }

  getProject() {
    return this.http.get(this.projectsUrl).map( res => res.json());
  }
}

TemplateHTML

<ng-container *ngFor="let project of projects; let i = index">
    <input type="text" placeholder="Title" value="{{ project.title }}">
    <input type="number" min="0" placeholder="Max. number of participants" value="{{ project.participants }}" >
    <input type="text" placeholder="Repository" value="{{ project.repository }}">


    <div class="langBox" *ngFor="let languaje of project.languajes; let i = index">
        <p > {{ languajes[i] }}</p>
    </div>


    <textarea name="" id="" placeholder="Write a description" >
        {{ project.description }}
    </textarea>
</ng-container>

Image