okamai naku (shite kudasai) - don't go through so much trouble, don't stress; often used if you're being served something as a guest
goenryo naku (shite kudasai) - don't hold back; ^ same scenario, host side

the (shite kudasai) is often left unsaid.

liiikewise,

enryoshite okimasu -- is pretty much the equivalent of "take a raincheck"

小山光さん おはよう!!

ano...ima gakko de nihongo o benkyou shiteimasu. yamashita tomohisa ga suki dakara nihon ni ikitai desu yo!! haha nihon no ryouri wa oishii desu ka?

そですか。日本のりょうりは大好きです。
So desu ka. Nihon no ryoori wa daisuki desu.
Oh really? I really like Japanese Cuisine!

Rondillo san,

watashi mo, nihon ryouri ga daisuki, demo sashimi ga anmari sukijanai desu. rondillo san wa? sashimi ga suki?

かわいいさん、さしみが大好きですよ！
おいしいんです。
Kawaii san, sashimi ga daisuki desu yo! oishiindesu.
I really like Sashimi! It is very tasty.

haha souka!! nihon ni ikimashita ka?? rondillo san, doko kara kimashita ka?? nan jin desu ka?

nihon ni ikimasen deshita. Kawaii san wa?

Doumo arigatou gozaimasu !!!!!! I really wanna learn japanese ,, hopefully i will take some classes during the summer vacation !!!!! i know the basics but i really wanna put a correct sentences and say it !!! heeehheee,, well that was really helpful !!!!!

is it enough for visiting japan?

I don't think so, because you will have to respond to the Japanese responses and you have to understand what they are saying, but it will help to know these expressions once you learn the language.