The only way to do this is to study! There's no one trick for everything. To remember word for a long time (=memorize) a good option to start with is cue cards, particularly for key words. You can create your own or use ones from an app such as Memrize or Anki and they work best if you do a bit every day and think about using them in sentences. When you get to a higher level you can probably stop using the cue cards and just start noting words you don't know as you come across them, looking them up and trying to use them. For pronunciation and speaking authentically (or fluently) the best thing for it is to practice, either by finding an online language partner or by taking some lessons. If you're practice with a partner or friend, make it clear to them that you want to know when you say something in the wrong way. If you can't find a language partner, or for extra practice in between, I really recommend listening practice - as you hear and identify words, you will learn how to pronounce them. There's an app called Audible which has a huge number of English-language audio books. I think you have to pay, but then you can just download all the free books and cancel your subscription ;) I recommend it because it has functions allowing you to slow down the speed to make it easier to understand, and it's easy to skip back 30 seconds if you miss something. If you don't want to pay there's countless Youtube videos about anything that might interest you, or you can listen to the radio (BBC iPlayer radio 4 has super-clear British pronunciation). Above all if you're really serious about fluency, you need to be doing at least a little bit every day, say 10 minutes of cue cards, and backing that up with longer sessions as often as you can. Good luck!

thank u every much! i will try![emoji][emoji][emoji][emoji][emoji][emoji]•ᴗ•(๑`･ᴗ･´๑)