他のオプション、これも行けます。実は以上のコレクションは正しいだけど、少し不自然と思います。日本で五年生は"grad student/graduate student"でしょう？

The new semester has begun!!

I started class this week.
I’m in college studying pharmacology.
I'm a grad[uate] student now, so I have to start doing research.
I have a lot of things to learn.
It takes a lot out of me :(
But it's challenging and that's why research is such fun! ("so fun"はもっと自然と思います）
I'm going to keep working hard and doing my best ＼(^o^)／

My university has sterted !!

My university has started since this week.
I study pharmacy at the university.
I have to do research because I became fifth grade.
I have a lot of things to learn.
It took a lot out of me :(
But it's challenging and that's why research is such fun!
I'm going to keep doing hard＼(^o^)／

Correction:

I started attending University this week!  I am studying to become a Pharmacist.  Since I am in  the fifth grade, I have to do reasearch.  I have a lot to learn, and it takes a lot out of me.  It's challenging, but that's why I think it's fun!  I'm going to keep working hard!

My university has sterted !!

My university has started since this week.
I  am studying pharmacology at the university.
I have to do research because I got fifth grade.
I have lots of things to learn.
ItI''ll take great efforts.
But it's challenging and that's why research is such a fun!
I'm going to keep doing hard work.