Problems when running downloaded "Main" files

I cannot run most of “Mains” from downloaded unzipped files related to this training programme. First, StudioX tries to “restore dependencies” (it takes really long), and then returns the following message (I cannot upload here any files as a “new user”): ““Missing or invalid activity”: This activity is either missing or could not be loaded properly”". The debug window gives a lot of messages like “Could not find type …” and then referring to any possible activities…
If the unzipped folders and files should be saved under a certain path on own PC, please provide with the path logic.