Let's just begin with simple words or phrases for everyday conversation.

Ha i - Yes
Ii e - No

Arigato - Thank you

O Genki Deska - How are you ?

I chi - One
Ni - Two
San - Three
Si - Four
Go - Five
Roku - Six
Shich - Seven
Hachi - Eight
Kyuu - Nine
Juu - Ten

Doitashimashite - You're Welcome

Hajimemashite - Nice to meet you

Ohayo - Good Morning (informal)
Ohaya Gozaimasu - Good Morning (formal)

Konichiwa - Hello or Good Afternoon

Konbanwa - Good Evening

Oyasuminasai - Good Night

Sayonara - Good Bye

Sumimasen - Means different things... Excuse me, Thank you, I'm sorry, and Pardon Me

Watashi wa ...... desu - I am .......

however in a normal, standard conversation you just say

................ desu

O namaewa nan desuka - What's your name ?

Nihon - Japan
Nihon Jin - Japanese

When you go a restaurant or stores in Japan, they often greet you with 'Irasshaimase' which means 'welcome. '

ikura - how much ?

That's all for now