My Mac is stuck on the loading phase of the reinstallation. It never finishes installing

Got it, please follow the directions in Mac Startup Screens and if those do not work, then please make an appointment at your local Apple Authorized Service Provider to have the computer professionally diagnosed.

Please read Writing an effective Apple Support Communities Question and then re-write your question. We are not mind readers or clairvoyants and cannot look over your shoulder so we rely on you to write an effective question that fully describes the issue you are encountering. Without fundamentals all we can do is guess what you are encountering which is not productive for you or us. 

In short we need specifics and not generalities in order to help you out.