Coco, I have practiced with many Asians, and I have never thought any accent was "weird". Grammatical errors are not a significant issue, as those end up being corrected over time. I enjoy practicing with all of my students.

Hi, I am pretty sure that they are not annoyed. About idioms and slangs,It is hard to teach a foreigner idioms and slangs, since most of them are not learned in a text book. Just watch alot of movies and TV shows and you will learn them soon enough. Lastly, most people aren't going to correct your sentences if they understand the context or the meaning of what you said. It is because it can come off as patronizing or belittling. If you want correction, simply ask them to correct them. or show your friends that you want to be corrected.

Hi! I don't think native speakers get annoyed by that... they are rather glad you are learning their language. It's natural for people to use slangs and idioms, but you can ask them to explain these to you, or watch lots videos & films, where these are likely to occur. This way you can learn them effortlessly.

Your friends are probably not annoyed (if they are good friends). As a native speaker with a lot of international friends, I can say that it is difficult to know that a friend is left out of the conversation because of the english I use. Likely, your friends do not realize that they are using a lot of slang. If you want to learn from them, you can ask them to explain what they mean, and also to correct you. They might think *you* will get annoyed if they correct you. Although, honestly, some native speakers will assume people who aren't completely fluent are unintelligent. Those people are ignorant, so don't worry about them. =) Also a small note: "Native Americans" often refers to indigenous Americans, also known as "indians" (not people from India). You could say: "Americans who are native speakers of english."