Could I learn Polish?

Well, I'm interested in learning Polish for a couple reasons. I know how difficult it is, so I'm worried it may be too difficult for me! Of course, I'd be prepared to put in the effort and dedication to learn this language, I already know a few words and things. I'm from Britain, so I'm a native English speaker, and I'm still a teenager.

My question: Do you know of anyone who has learned/is learning Polish successfully? How difficult is it?

If you are Polish, how do you feel about someone trying to learn your language? Is it even worth trying?

I just talked to my aunt and she said she'll let her daughter (my cousin) paint her nails as long as the colors don't make her look mature like a teenager or an adult.

I'm thinking of getting my cousin pastel colors. What other colors should I get her? What colors should she stay away from? Are neon or bright colors okay for an 8 year old?
I gave my cousin a pack of nail polish last week, but her mother made her give it back to me and I gave that pack away to my niece.