If your 7 friends don't show you that you exist and don't make you feel, you are important to them caring of you. It means they are no true friends. If you want to have a true friend which is here for you and prove it then tame me and adopt me as friend. Have you ever read "the little prince" by Saint Exupery ? If you have the patience to read it till the end, you will be pleased with it and you will understand how a true friend should be. I can help you to learn German because it's the first foreign language I learn I have the lever C1 French is my mother tongue. I wish you will read my message and my be answer me
It's the word to use when speaking about a number of people. I might be wrong but from what I understand you always need such a word when describing a specific number of things. Just like in English when you say "two pieces of cake" or "four sheets of paper". I hope that clears things up a bit and if anyone who is actually competent in Korean feels the need to add something to that, by all means, go ahead!