First of all you dont have to hate other ethnicities to love your own, you should be proud of your ethnicity but at the same time respect others. There are many people in afghanistan that are mixed, one of them is double abdullah, his father is panjshiri and mother is a pashtun, he knows how to speak both languages. There are also many people in Pakistan that are mixed with Panjabis and Sindis. There are many Pashtuns in Karachi that dont speak pashto, there are many pashtuns in Kabul that dont speak pashto, its not their fault, the language in their environment and education is something else.
The reason Farsi is more advansed in Afghanistan because its literature is rich, but at the same time alot of pashtuns and farsiwans dont realize is that there is alot of arabic that is used in what we call farsi especially in iran. Alot of the old farsi words are no longer used and instead they use arabic words. Pashto is a very rich language but it has been on the decline because all the institutions that once existed to advance the language have been destroyed.
On the other side of the Durand line, Pashto is also on the decline, There are no schools teaching pashto literature, English (British colonial) and Urdo (Moghuls) are the dominent languages. When ever a colonial power comes to a region, They will try to influence the local population with their own culture and language and they do it by building schools and institutions that serve the public.
You will start seeing English being spoken more and more in Afghanistan because the americans are building schools and institutions that will influence the local population with their culture and language.