I just bought a TFT screen is it still possible to use the serial port 1 and 0?
Yes, you can use those pins. Just because there are physical pins on the shield doesn't mean they are actually used. If nothing is written next to them then yes you can use them.

Be warned though that those pins are used for communication with your PC - and that includes uploading sketches - so you may experience problems doing things like that while your Mega is connected to those pins.