Learn Turkish: Bayram için geldik. Hoş geldiniz, iyi bayramlar! - "We came for bayram." "Welcome, happy bayram!"

The word için (for) only requires the genitive case (like the -in / -ın ending) when it is used with pronouns, such as benim için (for me) or senin için (for you). With regular nouns like bayram, you just use the plain noun.

Does bayram mean any kind of holiday?

Bayram specifically refers to major national or religious festivals in Turkey, such as Republic Day or the Eid holidays (like Ramazan Bayramı). If you are talking about a personal vacation, a weekend getaway, or a school break, you would use the word tatil instead.

Why is bayramlar plural in iyi bayramlar?

In Turkish, well-wishes and greetings are almost always pluralized. Just like you say iyi günler (have a good day, literally 'good days') or tebrikler (congratulations), you use the plural -lar suffix for holiday greetings to express abundance.

Why is Hoş geldiniz (Welcome) in the past tense?

Literally, hoş geldiniz means 'you came pleasantly' (hoş + gel-di-niz). Because the person has already completed the action of arriving by the time you are greeting them, Turkish naturally uses the definite past tense to say 'welcome'.