Some questions .

1, about the australian content

https://steamcommunity.com/sharedfiles/filedetails/?id=1778501667

Are there high quality freeware routes / sessions on the DLS or on the web that are worth to download ?

2, Where can i download this route ?

There's Illawarra South Coast, Goulburn Murray Lines v4, ARTC Main South-VR Northeast that I have built. Sessions for Illawarra begin with ISCNSW. All are quite large.
Good routes by other authors are: QR Kingaroy Proston Branch, NSW Great Northern, NSW Cooma - Bombala, Pilbara Iron, etc.
All are on the DLS. With my routes, see the launch pages in Freeware releases which will link most of the non DLS assets, particularly for the Illawarra route.
The DLS has a plethora of locomotives and rolling stock for Aussie routes.
https://forums.auran.com/trainz/showthread.php?165104-Illawarra-South-Coast-NSW-Australia
https://forums.auran.com/trainz/showthread.php?164092-VR-Goulburn-Murray-Lines-v4-0
https://forums.auran.com/trainz/showthread.php?141534-ARTC-NSW-MAIN-SOUTH-VR-NORTH-EAST-ROUTE

Cheers Graeme

Thank you .

The Blue Mountain route is also a very large and excellent route, but it has a missing dependency that is the Sydney Opera House that the creator will not release and no one else has made another model of.

If you are interested in Narrow Gauge (3ft 6in) steam era, then

South Australia - https://forums.auran.com/trainz/showthread.php?163601

Tasmania - https://forums.auran.com/trainz/showthread.php?142493