SIM800C-DS power supply schematic
This is the power supply schematic provided in the datasheet, SIM800C-DS_Hardware_Design_V1.00, to which you refer. See section 4.1



So, yes, it would appear that your drawn schematic is correct.

From section 4.1.1


  Pin34 and Pin35 are VBAT input, Pin36 and Pin37 are GND of power supply, and VRTC pin is power supply of
  the RTC circuit in the module. VDD_EXT output 2.8V when module is in normal operation mode. 


From section 4.2.1


  Customer can power on SIM800C-DS by pulling down the PWRKEY pin for at least 1 second and release. This
  pin is already pulled up to 3V in the module internal, so external pull up is not necessary. Reference circuits are
  shown as below. 




Your schematic differs slightly  in this respect. Try building it and see what happens, or ask the person who drew it, why they differed from the PWRKEY in the schematic.