A postán a díj a csomag súlyától függ.

Postán means at the post office (more literally, at the post). It’s posta + the place ending -n (a form of the superessive case, often used with certain institutions/places in idiomatic Hungarian).

• posta = post office
• -n here ≈ at/on (idiomatic location)
• a postán = at the post office (the post office as a known place in context)

You’ll also see other location endings depending on the noun (e.g., bankban = in the bank, iskolában = in the school), so this is partly something you learn noun-by-noun.

Hungarian uses the definite article a/az very frequently, often where English might omit the.

In this sentence:

• A postán = At the post office (definite place)
• a díj = the fee
• a csomag súlyától = on the package’s weight (literally: from the package’s weight)

So it’s normal to have multiple a’s: each noun phrase can take its own article.

The subject is a díj (the fee). Hungarian verb agreement is with the subject, and a díj is third-person singular, so:

• (a díj) függ = (the fee) depends

függ is the present tense, 3rd person singular form of függni (to depend / to hang).

The basic pattern is:

• X Y-tól / Y-től függ = X depends on Y

So Hungarian uses the ending -tól/-től (often taught as “from”) after the thing you depend on.

In your sentence:

• a díj … függ = the fee depends
• a csomag súlyától = on the package’s weight (using -tól)

Yes—Hungarian builds “the package’s weight” with a possessive ending, then adds the case ending needed by the verb.

a csomag súlyától =

• a csomag = the package
• súly-a = its weight / the weight of it (3rd person possessive: “package’s”)
• súly-á-tól = from its weight (possessive + case ending)

So the structure is essentially:

• (the package) (its weight) (from)

This is the normal Hungarian way to say the weight of the package without using a separate word for of.

That’s vowel harmony. Hungarian chooses the vowel in many endings based on the vowels in the word.

• -tól is used after back-vowel words
• -től is used after front-vowel words

súly contains ú (a back vowel), so it takes -tól:

• súly + -tól → súlytól (and here with possessive: súlyától)

The word order is flexible. Putting A postán first sets the scene/topic: as for the post office…

Other natural word orders include:

• A díj a postán a csomag súlyától függ. (more neutral “the fee” first)
• A csomag súlyától függ a díj a postán. (emphasizes weight as the key factor)

Hungarian word order often reflects what you want to emphasize, not just grammar.

You can, but it changes the meaning/feel.

• A postán a díj… = At the post office, the fee… (a specific, known fee—e.g., the postage fee)
• A postán egy díj… = At the post office, a fee… (more like “there is a fee that…”, introducing it as new/one of many)

Dropping articles entirely is usually not natural in Hungarian unless you’re using a special style (headlines, notes).

Common distinctions:

• díj = fee/charge (often for a service; very natural for postal services)
• ár = price (more like the price of a product or a listed price)
• költség = cost/expense (broader, can be your cost rather than a fee charged)

For postage, díj is a very typical choice.

A few common ones:

• díj: long í (hold it a bit longer)
• cs in csomag: like English ch in chat
• súly: s is like English sh (so súly starts with sh), and ú is long
• gy doesn’t appear here, but függ has doubled gg, which is held slightly longer than a single g
• Stress is usually on the first syllable of each word: PÓstán, DÍJ, CSOmag, SÚlyától, FÜGG