My fFavorite aArtist My Favorite Artist

My fFavorite aMusic Artist My Favorite Music Artist

(1) Generally, all words in a title are capitalised. Minor issue though. (2) "Artist" is a very broad term. It'd be good to specify explicitly that you're referring to music artists in particular.

My fFavorite aArtist My Favorite Artist

My favorite music artist is Kenshi Yonezu. My favorite music artist is Kenshi Yonezu.

Same as above.

I think he is most famous artist in Japan. I think he is most famous artist in Japan.

I think he is THE most famous artist in Japan

I think he is the most famous artist in Japan. I think he is the most famous artist in Japan.

I think he is the most famous artist in Japan. I think he is the most famous artist in Japan.

I think he is the most famous artist in Japan. I think he is the most famous artist in Japan.

I love his song, "Junk". I love his song "Junk".

I love his song, "Junk". I love his song, "Junk".

A space is placed after commas.

I love his song, "Junk". I love his song, "Junk".

It is very sad song, and very emotional. It is very sad song, and very emotional.

It is A very sad song, and very emotional

It is very sad song, and veryand emotional song. It is very sad and emotional song.

It is a very sad song, and very emotional. It is a very sad song, and very emotional.

It is a very sad song, and very emotional. It is a very sad song, and very emotional.

You could also say "It is a very sad and emotional song."

I have been waiting his song forever. I have been waiting his song forever.

I have been waiting FOR his song forever

I have been for waiting his song forever. I have been for waiting his song forever.

I have been waiting hisfor his (new?) song forever. I have been waiting for his (new?) song forever.

(1) The phrase is "wait for (something)". (2) It's not clear what song you're waiting for. Are you referring to "Junk", another new and upcoming song, or something else? It doesn't make sense to wait for "Junk", since it's already been released, so I'm assuming that you're referring to a new song, in which case it'd be good to clarify this.

I have been waiting hisfor his (?) song forever. I have been waiting for his (?) song forever.

I'm not quite sure what you mean here. If you're referring to the song you already mentioned, you could say "I have been waiting for this song forever." if it came out recently. If it wasn't a recent release, you could say "I waited for that song forever."

I have been waitinglistening to his song forever. I have been listening to his song forever.