It sounds like 마리야, but it is written 말이야. I've got a reference for your question to explain in detail. http://krdic.naver.com/rescript_detail.nhn?seq=6250 말이야', '말이죠', '말이지', '말인데' are all synonyms that are expressed when drawing someone's attention and make a promise. ex) 음식도 맛있고 말이야 - without 말이야, the sentence still makes sense on its own. However, 말이야 is a good way to make the sentence sound more interesting.

As my heart follows it.

That's an interesting question. I am not sure if there are any further detailed answer to your question, but as far as I am concerned as a Korean, let me try to explain about it. It basically is used to inform and rather sound like an order. You don't really hear that kind of sentence on a daily basis unless you are talking to older people with high authority. It isn't really informal, whereas you've got to be careful when to use according to the person you are talking to. Also, i would not say it is rude as long as you don't say it to older people than you and someone you are not close to. Hope this helps and have fun with learning korean :)

wow. You've watched really many dramas! impressive :D

which one is your favourite? 

Yeah i understand what you are feeling like because that is what i normally felt when l was learning english. I still have problems in terms of listening, but by the time i have tried to figure it out, it has been much better than before. Apparently, teachers speak clearly when teaching, however as you already know, each person has his or her different pronunciation. That is why it could be challenging to understand korean apart from korean teachers. In my opinion, watching dramas or movies with subs is more effective than watching with non subs as you can notice what they are saying. Another advantage is that whenever you do not properly understand what's going on, you can try to hear and read subtitles over and over. This is what people often do when learning english. One thing you need to bear in mind is not to hurry. Don't too much push yourself under pressure when learning another language. This would provide you with stress and therefore you will be more likely to be fed up with Korean. I guess there are many kind korean people on italki who are willing to help you with learning korean! Hope you enjoy studying korean :) good luck!