I am a beginner in web development, and now I am in training and I was asked to create a web application, knowing that they do not have a server. is it there's a solution?
You can use your computer as a server (provider of you web application) during the training. If you need to make the app available in long term or for more users, you can always host it in providers like Amazon.
If you need help to configure your pc as a server, please provide more information (what tecnology are you learning? What should the web application do?).