it all depends with whom you are conversing...

If this is a friend of yours, a person whom you know well and with whom you are in a good relationship, your peer,
then you would indeed say CZEŚĆ.

However, CZEŚĆ is more similar to HI.

CZEŚĆ contains two special Polish characters at the end. They look like an s with an apostrophe above and an c with ah apostrophe above.

It may be rather hard to pronounce, as the special characters I told you about have no phonetic equivalent in English.

"Cz" is pronounced like "tch" in ITCH
"e" is pronounced like e in PET
"s" with apostrophe is pronounced like sh in SHEET, but much much softer
"c" with apostrophe is pronounced like ch in in CHEAT, but much much softer

Polish is more formal, more indirect than English. If you are talking to someone who is older than you, or with higher status, you would not say CZEŚĆ to them. It would be dropping the ball...

To avoid this, it is best to use the word WITAM. It is pretty neutral and can be readily used in both contexts.

In Poland we are often in a situation when we have known someone for some time, are in a good relationship, but we are unsure whether we could switch from the formal mode to the friendly one. When we are meeting such person, we feel uncomfortable because we do not know if we should stay formal or cross the border and switch to the friendly mode. WITAM (pronounced like VEE-TUM)is perfectly suited for this situation.