In addition, the above will, for every sentence that arrives display a pile of stuff on the serial monitor and write a heap of stuff to SD card. On most GPSs there are about 10 sentences a second and only two of them contain location data, so most of the time you displaying and writing stuff to SD that has not changed.
Then there is the time one of these updates takes, the software serial buffer is only 32 bytes long which @ 9600baud is around 33mS, so if all the serial printing and SD writing takes longer than that you will miss sentences from the GPS, you might never get a fix ........... so you need to re-organise how your reading the GPS.