listing sd card files on a tft screen
If I start listing the files, can I scroll up and down ? Because at some point the TFT screen will become full of text, and I don't want the text to be overwritten.


If you program that kind of facility, yes. 

A TFT screen is like a blank piece of paper, and you have a set of crayons. You draw on the screen (sometimes with pre-defined shapes, called "letters"). If you want to change what is on the screen you can either throw away your piece or paper and start with a new blank page, or you can get some Tip-Ex® and cover up parts that were there already so you can draw over them.

If you want scrolling you will have to work out for yourself how best to do that given the limited resources you have available.

The simplest method is just to retain a list of the filenames in memory and print just a subset of them on the screen. "Scrolling" then just means displaying a different subset of names.