We will try to visit Afghanistan during Stanexpress.
As you know the situation in the country is not really safe, but there are some areas which are relatively safe for visiting. The areas would be around Herat, Masar-e Scharif and Wakhan Corridor.
Regards the visa: What we could find out is, you can get a visa. It´s just quiet expensive and sometimes the afghan Embassy is asking for a letter for your countries embassy. But the situation is changing regularly and it doesn´t make to much sense to focus now on it.
With in the time you will see the information displaying on this page.
In between we recommend you the page https://www.lostwithpurpose.com