You can run the desktop modeler to start your app locally.
I can stongly advise you to complete some learning paths
F5 should be your favourite hotkey!
but how can i execute the app without loading the app in the cloud? (without the modeler)
Why do you want that?
Do you know you can set the modeler with a security level, off, prototype/dem and production to build your environment?
Try the learning path https://gettingstarted.mendixcloud.com/link/home
I guess you can't download the environment localhost, because of the security setting. but maybe i'm wrong?
Or do you just want to know how to set up a localhost environment?