I'm still unsure about what exactly you want to do. Do you want just the very first path name renamed to the one you selected? Here are some changes I would make to the script:
Turn off dialogs.
Add PSD save options - I'm assuming you want them saved as psd.
Add dialog to select a save to folder
Get rid of second loop that goes through the paths.
Add a try/catch block so you don't get error messages
Add a save as to save the file to a new location.
Change SAVECHANGES to DONOTSAVECHANGES to get rid of extra dialog that you don't need.
#target photoshop
app.displayDialogs = DialogModes.NO;
var psdOptions = new PhotoshopSaveOptions()
psdOptions.layers = true
var selFolder = Folder.selectDialog( 'Location of images to process...' );
var saveFolder = Folder.selectDialog('Path for save folder');
var files = selFolder.getFiles ( /\.jpg$/i );// may need to edit for different formats;
var newPathName = prompt ("Pfadnamen eintragen", 'Proll', "Pfad 1");
for(var f = 0; f < files.length; f++ ){
var doc = app.open( files[f] );
var numberOfPaths = doc.pathItems.length;
try{
if( doc.pathItems[0].kind == PathKind.NORMALPATH && newPathName != doc.pathItems[0].name ) doc.pathItems[0].name = newPathName;
}//end try
catch(e){}
}//end for loop
doc.saveAs (new File(saveFolder +'/' + doc.name), psdOptions)
doc.close(SaveOptions.DONOTSAVECHANGES);
}