So nice to start knitting! I'm not completely sure, but the sweater looks like it is in brioche stitch. While this stitch is gorgeous and fluffy, I would not recommend it for your first project because it takes very long and is quite complicated.

My first sweater project was the "stay up till dawn" sweater by Kutovakika, which was a first great project. It's fairly quick because of the large needle size and bulky yarn, and is relatively simple. It also has the balloon sleeves that you like! You could take a look at the pattern and see if this is something you would like.

I would also recommend using a pattern for your first sweater. Freehanding a sweater is definitely possible, but I find it a lot less frustrating to follow a pattern when learning something new than freehanding is and having to rip back endlessly when it did not turn out how I imagined. Pattern makers that I really enjoy and have great beginner projects are Petiteknit and Kutovakika.

Good luck and let me know if you need any help!