Don't stress, you'll be fine! :-)
With all of us helping you know it will be great. LOL
You need to iron the t-shirt fabric onto a stabiliser before you cut it up. I used a very thin iron-on interfacing, you would have something similar over there. It holds the fabric firm so that when you cut your pieces out they don't distort or stretch.
You still need to be careful with your pieces and not stretch them.
Do you have a pattern in mind?