Learn Hardcore Turkish: Eski ahırda saman balyaları yığın halinde duruyor.

-da is the locative case suffix, meaning “in/at/on.” Ahır = “barn,” so ahırda = “in the barn.” Eski (“old”) simply modifies ahır, giving eski ahırda = “in the old barn.”

Why does saman balyaları end in -ları? Is it marking plural, accusative, or possession?

Here saman balyası is a fixed genitive–possessive compound meaning “bale of hay” (literally saman + (ın) balyası). The -sı is the 3rd-person singular possessive built into that compound. When you pluralize it, you add -lar and then the suffix vowel -ı again (both steps obey vowel harmony):
saman balyası → saman balyaları (“hay bales”).
This is not the accusative case but simply the plural form of the compound noun, which functions as the subject of duruyor.

What is yığın halde, and how is it formed?

Yığın means “pile” or “heap.” The suffix -hâlde (from hal “state/condition”) turns a noun into “in the state of X.” So yığın halinde = “in the state/condition of a pile,” i.e. “piled up” or “in heap form.”

Why is the verb duruyor used here instead of something like var or bulunuyor?

Durmak can mean “to stand” or “to be positioned upright” (not only “to stop”). With inanimate objects, duruyor describes them as “standing” or “set up.” So saman balyaları … duruyor conveys “the hay bales are standing/piled up.”

Why doesn’t the verb show plural agreement (e.g. duruyorlar)?

In modern Turkish, the 3rd-person singular continuous ending -yor often covers both singular and plural subjects. Adding -lar (making duruyorlar) is grammatically possible but usually omitted in neutral descriptive sentences.

Where are the articles the or a/an in Turkish?

Turkish has no articles like the or a/an. Definiteness or indefiniteness is understood from context, word order, or case markings (e.g. the accusative can mark a definite direct object). In this sentence, there’s simply a descriptive statement, so no article is needed.

Is the word order fixed? Could I say Saman balyaları yığın halinde eski ahırda duruyor?

Yes, Turkish word order is relatively flexible. The typical pattern is Subject–Place–Manner–Verb, but you can reorder elements for emphasis. Putting eski ahırda at the front highlights “in the old barn”; moving it later still works but shifts focus slightly.