First post!

This is my first post! But I don't know what to write down here.
Ah...
Recently I have watched the world cup every morning. Of course I know Japan is not strong but I don't care because I love to watch nice games.

 

あなたの英語をなおしています。とてもよくできています！

First post!

 

This is the first post!

"the first post" means the first post on italki unless you have talked about multiple posts you have made before (for example, "I have made five posts on italki and is the first post."), so you should say "my first post" instead.

But I don't know what I write down here.

Try to not start sentences with "but", especially when the sentence (and the one before it) are so short. Also, it is better to remove "down". "write down" is better when you are writing on paper. "what I write" should be: "what I can write", "what I want to write", "what to write", etc.

Ah...
Recently I have watched world cup every morning.

It should be "the World Cup" with capital letters, because it's the name of the event.

Of cause I know Japan is not strong but I don't care because I love to watch nice game.

"Of course,..." and you can say "nice games", but it's better to say "good games" - or instead of using "games" say "watch a...".

 

 

Example correction:

This is my first post, but I don't know what to write here.
Ah...
Recently I have watched the World Cup every morning. Of course, I know Japan is not strong but I don't care because I love to watch a good game.

First post! Welcome!

This is the my first post! But I don't know what I should write down here.
Ah...
Recently I have watched The World Cup every morning. Of course cause I know Japan is not a strong team (or Japan is not very good), but I don't care, because I love to watch a good nice game.

Great job! Welcome!

First post!

Although this is my first post, I am not quite sure what I wish to write about.
Ah...
Recently I have been watching the world cup every morning. Even though I know the Japanese team is not that strong, I still love to watch the games.