ADMIN will certainly give you a good advice, but i can also give you my humble suggestion.
I was also in the same situation last year, i can speak pashto fluently but was not able to write it. Then i started practicing and wrote 2-3 pages daily, after 10-12 days i was able to write it fluently without many errors, so you can opt pashto, its high scoring and also easy to cover the entire course. I attempted the whole paper in CSS-2012 except 2 proverbs and 2-3 objectives/mcqs.
Regards