how do I get the long distance bus from nanning guangxi to Qishazhen gangkou Qu Fangchenggang Shi Gu

There is no long distance bus from Nanning to Qishazhen. But you could get there by train. Take a train at East Train Station in Naning, and get off at North Fangcheng Port. Then take bus 6 and get off at Zhongzhi Xinggang Huafu Station. After that, take bus 103 and get off at Qisha Town. Then walk 760 yards south and you will arrive.