asifbhutto You can use rss feed reader (local on you PC or as an internet service) to monitor sub categories like
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RSS feed reader are monitoring such urls and read them in a defined interval. These urls contain a XML file with all needed information about the newly posted topics.
Within the RSS feed reader you can define your own search criteria to get only the new topics you are interested in.
I'm using a RSS feed reader on my PC.
It looks like this:
You can see there are thousends of posted courses and by setting the search/filter to "python" I will see all new threads that contain the word "python" in it.
You can click on the entry and see the main information about that particular post at the bottom of the program. By double clicking the thread can be opened in the browser and you can start your download there.
This is only 1 example of many many other programs and services that do the same job.