You are right. There are many different ways to say the same things in English. It is best to first learn the most common ways of speaking, but it is also good to at least familiarize yourself with the other words/expressions so you will understand them when you hear them. You don't need to try to use the complicated ones when you speak (at least not yet), but if you are familiar with them, you will understand them when you hear native speakers say them. This will help you become more comfortable with them and learn more over time. For improving your accent, the two main pieces of advice I can give you are: 1. Watch how native speakers move their mouth. Is there mouth open wide for certain sounds, or is there mouth small and narrow? How are they moving their jaw? Which part of the mouth is the focus of the sound? Look for videos in English on youtube, or just watch English TV shows or movies. 2. Mass listening. This means listen to English native speakers a LOT. As often as possible. In the car, on the train, walking down the street, lying in bed (basically anywhere you can). Even if you're not paying attention, it will soak into your subconscious mind. You will also learn new words and expressions from the context without even trying to actively learn them. You can download many podcasts from iTunes for free or find videos on youtube. Look for news or discussions. These will have a wide variety of expressions, accents, and vocabulary. Even if you do not understand much of it right now, that's okay. It will help you a lot in the long term because your mind will become comfortable with the language.

I agree that English has too many words with the same meaning. I blame Shakespeare. I would just learn the most common ones if I were you. If you want to work on your accent and pronunciation try mimicking native English speakers. It's going to take a lot of "acting" because you won't feel comfortable saying it in your normal dialect. Look at it as adopting a new "North American" personality when you speak English.

1) Concentrate on the words you actually hear used in conversation or see in newspapers, magazines, and contemporary books/novels. There are a lot of words in older books and dictionaries that you'll never use in real life. If a word has a lot of different meanings, just memorize the one that fits the context in which you heard or read it. ("In this case, the meaning must be...") 2) To improve your pronunciation, watch the mouths of native speakers when they talk. (This is how I learned that Japanese was spoken with a much "flatter", less rounded mouth than English.) When listening to podcasts or watching TV/movies in your target language, try to mimic the voices of the speakers as well as the words and expressions they use. (Have you ever mimicked a friend's voice or way of speaking?) This will help you develop your vocal range in the language, and force you to pick up on things you might be missing. (I'll say "book" and my Japanese friend will say "bukku"...until I force him or her to mimic me, instead of just saying what he or she "thinks" I'm saying.) For practicing individual English speech sounds, this is a great resource: http://www.uiowa.edu/~acadtech/phonetics/english/frameset.html They have a mobile app available as well. Good luck on your journey to English mastery! ;)

You'll be building your vocabulary for the rest of your life (like native speakers), so please don't think there's a target number of words. There's just a lot more to learn at the beginning. Take it all in. Don't dismiss words because you think they're not "common" enough. I see students deliberately do this and then wonder why they don't make any progress. Speak DIRECTLY to native speakers. Remember that media (books, TV, movies, radio) are all constructed, polished and re-polished presentations. You'll only find out what the native speaking habits and preferred words are by speaking directly to people. As for the accent, always remember to relax. You'll most likely pick up an accent from the people you speak to (yes, you should do this), so listen to how they speak and also listen to how you sound. You can hire a teacher or tutor to pay attention to your speaking habits, give you feedback and help you correct any problems.

I would not bother trying to memorize all of the words in the English language. Since North America has a vocabulary that seems to be "shrinking" and using less words. I would just learn the common words and phrases we use today. If there is a topic that interests you, learn more words from that topic. For helping with your accent and pronunciation, just keep trying to speak out load as much as possible. pay very close attention to how you sound compared to a native. Maybe listening to music and singing along with the song will help you accent. Try to mimic all of the words in the song exactly as they are said.