Kasiyere kolay gelsin dedim.

Because kasiyere has the dative case ending -e, which often means to or toward someone.

• kasiyer = cashier
• kasiyere = to the cashier

In this sentence, the person speaking is directing the expression kolay gelsin to the cashier, so Turkish uses the dative:

• Kasiyere kolay gelsin dedim. = I said kolay gelsin to the cashier.

Kolay gelsin is a very common Turkish expression said to someone who is working, busy, or doing a task. It means something like:

• May it go easily
• Hope your work goes smoothly
• Take it easy with your work

It is not usually translated literally in normal English. It is more of a polite social expression than a direct factual statement.

It is partly understandable literally, but in everyday use it works more like a fixed expression.

Word by word:

• kolay = easy
• gelsin = let it come / may it come

So literally it is something like may it come easy, but native speakers do not usually think of it that way. They understand it as a standard polite phrase used for someone who is working.

Dedim means I said.

It comes from the verb demek = to say.

Breakdown:

• de- = say
• -di = past tense
• -m = I

So:

• dedim = I said

This is a very common past-tense form in Turkish.

Because Turkish normally puts the main verb at the end of the sentence.

So the structure is:

• Kasiyere = to the cashier
• kolay gelsin = easy come / hope it goes easily
• dedim = I said

This end-position for the verb is one of the most basic features of Turkish sentence structure.

Because Turkish often leaves out the subject pronoun when it is already clear from the verb ending.

Here, dedim already means I said, so ben is unnecessary.

You could say:

• Ben kasiyere kolay gelsin dedim.

But usually ben would only be added for emphasis or contrast.

Yes, you could say just Kolay gelsin dedim if the context already makes it clear who you said it to.

• Kolay gelsin dedim. = I said kolay gelsin.

Adding kasiyere makes the listener know exactly who received the expression:

• Kasiyere kolay gelsin dedim. = I said it to the cashier.

Because Turkish usually expresses meanings like to, for, or toward with a case ending, not a separate preposition.

So English says:

• to the cashier

Turkish says:

• kasiyer + e → kasiyere

This is very typical in Turkish grammar.

Yes. That is very natural.

Turkish speakers commonly say kolay gelsin to people who are working, such as:

• cashiers
• shop workers
• office workers
• waiters
• repair workers
• drivers
• employees in general

So saying Kasiyere kolay gelsin dedim is socially natural and polite.

Not exactly in form, even though it contains what was said.

Turkish often puts the spoken words directly before dedim without needing punctuation in ordinary writing:

• Kasiyere kolay gelsin dedim.

This means:

• I said kolay gelsin to the cashier.

You may also see it written with punctuation in some contexts, for example in more careful writing:

• Kasiyere, kolay gelsin, dedim.
• Kasiyere kolay gelsin dedim.

But the version without punctuation is very normal.

A useful breakdown is:

• kasiyer-e = to the cashier
• kolay gelsin = may it go easily / hope it goes smoothly
• de-di-m = say-past-I

So very literally:

• To the cashier, “may it go easily,” I said.

But the natural English meaning is simply:

• I said “easy work” / “hope your work goes smoothly” to the cashier.
• Or more naturally: I said “kolay gelsin” to the cashier.

No, that would not be the normal way to say it.

için usually means for in the sense of for the benefit of, for the sake of, or intended for. Here you are speaking to someone, so the dative is the correct choice:

• kasiyere = to the cashier

So the natural sentence is:

• Kasiyere kolay gelsin dedim.