Hi, I'm not an expert, in fact I was searching for info to write a motivational letter myself, but seeing as no one responded to you, let me make a few corrections of your English:
"In my last semester I had the chance enroll in the..." - Last semester I had the opportunity to enroll...
"It made very much fun to work with them." - It was a lot of fun working with them.
"For over two years I am an entrepreneur" - maybe: I've been an entrepreneur for over two years
I run, successfully, an online shop that sells hairpieces. <- + the commas
"Due to my interest... ...Australia with its history and the current situation meets all of these demands." - Australia seems to be the perfect place for me. (or something)
You use the word "University" to much in the last couple of lines.
Best of luck.