Greek is definitely a difficult language but learning to use some words in your holiday is easier that what you think.
Survival
Yes: neh (this should be confusing for people knowing a bit of bavarian… cause it means no!)
No: oh-hee
Help: Voh-ee-thee-ah
I do not understand: Then kah-tah-lah-véh-noh
I do not know: Then xé-roe
Ups!: Oh-pah
Greetings
Good morning: kah-li-mé-rah
Good evening and good afternoon: kah-lee-spé-rah (when you meet people or entering a place) and kah-lo apo-gheu-mah (mostly when you leave a place)
Good night: kah-lee-neé-chtah (but this is being used when you are leaving a place, not while entering or meeting people)
Hello and goodbye: yah or yassoo (when you talk to a young person or someone you know) and yassas (formal form of hello)
See you or talk to you later: Tah léh-meh
Being polite
Thank you: Eff-kha-ri-stó
Please and you are welcome: pa-ra-kah-ló
Sorry/ Excuse me: See-ghnó-mee
Nice to meet you: he-ro po-lee
How are you?: tee kah-nis? (when you know someone) and tee kah-nee-tee? (formal way)
What is your name?: Pos se léh-neh (informal) and pos sas léh-neh? (formal way)
Giving basic replies
ok: e-nta-ksi
everything is ok: ola kala
perfect: te-li-a
I am fine: i- me kala
I am ok: i-me ok
so and so: e-tsi ke e-tsi
Not bad: oh-hee ke as-hi-ma
I am not ok: den i-me kala
My name is: To o-no-ma mu i-ne … or me léh-neh …