Neha, give my greatest regards & concern to your father..how the cancer can go from stage two to four that quickly is beyond comprehension but having all the treatments he has & is doing is the only way to beat it. As far as speech & swallowing, "time will heal all wounds"
After my partial glossectomy it took at least a month to even use the muscles that bring liquids or food to the back of the throat, now it seems I can get it there but it doesnt want to go down always. There are brighter days ahead for your dad and its amazing what people can understand without being able to enunciate clearly...we speak the language of humanity. Well wishes to him.
Love Maria