You can flash your Nokia phone using different flashing boxes, e.g UFS, Phoenix, ATF. Before flashing process don't forgot to get backup of your important data, because after flashing process you all important data will deleted.
Nokia 305 released on April 2014, and it is developed by Nokia. Nokia 305 dual sim phone goes to BB5 group. The flash file of this Nokia phone are of low size, and fast to download, you can download it in a couple of minutes.
Download Link (V-7.8)
MCU (28 mb)
PPM (8 mb)
and tested
Old Version