I'm not sure what you have in mind when you say you want to make the paragraph more sophisticated, but if you want to improve it, I would suggest making it simpler. Many people, even native speakers of English who are well into adulthood, believe they should use complicated sentences and long, obscure words if they want to sound intelligent and well-educated. But the goal of language is to communicate ideas, and it's often better to use simple, clear writing that gets your point across quickly and accurately.
I have the intention of improving this paper
is wordy and indirect, and sounds weak. You can change it to
I intend to improve this paper
which is simpler and more direct, and communicates an active intention ("I intend") rather than a passive state of being ("I have the intention"), which makes it a stronger sentence.
and I want to do this Improve in one of these 3 subjects
There are several problems here. It is ungrammatical: either "Improve" should be "improvement," or you should say "I want to improve...". Also, presumably, you want to improve in all three areas, not just one of them. Most importantly, though, most of these words are entirely unnecessary. Why not just say:
in three subjects
which, again, is much simpler, more direct, stronger, and easier to understand. Putting the two parts together with one final change (from "subjects" to "subject areas"), we get:
I intend to improve this paper in three subject areas
In 10 words we've said the same thing that took us 21 words to say above, and it's a stronger sentence that requires less mental effort on the part of the audience to read. And that's the key to good writing!