Objective

My objective is to enlarge my vocabulary and improve my conversation. For this, I intend to read more books and watch more movies without legends subtitles.

You are using verb infinitives. Sentence could also be written '... is to enlarge ... and to improve ...' but the second 'to' is often not needed, it shares the first 'to'.

http://grammar.yourdictionary.com/parts-of-speech/verbs/infinitive-verb.html