I'm not sure how to answer "what do I like in my target language" because there are many things. One thing is that there are things in the languages I'm learning which make more sense to me, as in the way they function than in my native language, such as spelling in Spanish but then there are things I just don't find easy to grasp.
As for "does learning a new language change your understanding of the world"...Yes. This is one of the main reasons I study languages so that I can explore, understand different places, cultures and ways of thinking.