Než půjdu do obchodu, napíšu seznam: mrkev, kuře, těstoviny a chléb.

In this sentence, než means before.

Czech než has more than one use:

• in comparisons: větší než dům = bigger than a house
• in time clauses: Než půjdu do obchodu... = Before I go to the shop...

So here it introduces a time relationship: first I write the list, then I go to the shop.

Yes. Půjdu is the 1st person singular future of jít (to go on foot).

This verb is irregular, so its future is not formed in a simple predictable way. The forms are:

• půjdu = I will go
• půjdeš = you will go
• půjde = he/she/it will go
• půjdeme = we will go
• půjdete = you will go
• půjdou = they will go

So Než půjdu do obchodu... means Before I go / before I will go to the shop...

This is mainly about aspect, which is very important in Czech.

• psát = imperfective, to write / to be writing
• napsat = perfective, to write down / to finish writing

Napíšu is the present-form ending of a perfective verb, but perfective present forms usually have future meaning in Czech. So:

• napíšu seznam = I will write a list / I’ll write down a list
• píšu seznam = I am writing a list
• budu psát seznam = I will be writing a list or I’ll spend time writing a list

Here the idea is a single completed action before going to the shop, so napíšu is the natural choice.

Because the preposition do requires the genitive case.

The noun is:

• obchod = shop/store

After do, it changes to genitive singular:

• do obchodu = into/to the shop

This is a very common pattern:

• do domu = to the house/home
• do školy = to school
• do města = to the city

So půjdu do obchodu literally means something like I will go into the shop, but in normal English we translate it as I’ll go to the shop/store.

It is in the correct case: accusative. It just happens to look the same as the nominative.

Here seznam is the direct object of napíšu:

• napíšu co? → seznam

For many masculine inanimate nouns, nominative singular and accusative singular are identical:

• nominative: seznam
• accusative: seznam

So the form does not visibly change, even though its grammatical role does.

Because Czech usually omits subject pronouns when they are clear from the verb ending.

Both verbs already show I:

• půjdu = I will go
• napíšu = I will write

So já is unnecessary unless you want emphasis or contrast:

• Já napíšu seznam, ty nakoupíš. = I’ll write the list, you’ll do the shopping.

In neutral sentences, leaving out já sounds more natural.

Because Než půjdu do obchodu is a subordinate clause, and Czech normally separates subordinate clauses with a comma.

So the structure is:

• Než půjdu do obchodu, = subordinate clause
• napíšu seznam = main clause

This is standard Czech punctuation. English also often uses a comma when a clause like before I go to the store comes first.

The colon introduces the contents of the list.

So:

• napíšu seznam: = I’ll write a list:
• then the actual items follow: mrkev, kuře, těstoviny a chléb

This is very natural in Czech, especially when introducing examples, items, or explanations.

Because this is a list, and shopping-list items are usually given in their basic dictionary forms.

That means you often see nouns in nominative-style list form, even though in a full sentence they might appear in another case.

For example, in a full sentence you might say:

• Koupím mrkev, kuře, těstoviny a chléb. = I’ll buy carrots/a carrot, chicken, pasta, and bread.

A few useful notes:

• mrkev = carrot
• kuře = chicken
• těstoviny = pasta; this word is usually plural in Czech
• chléb = bread

So the list after the colon is not meant as a fully inflected sentence; it is just a written list of items.

In Czech, těstoviny is normally a plural noun when talking about pasta in general.

So Czech commonly says:

• mám rád těstoviny = I like pasta
• koupím těstoviny = I’ll buy pasta

Using a singular form here would sound unusual for the general food category. This is similar to how some nouns behave differently across languages: English uses singular pasta, while Czech usually uses plural těstoviny.

Yes, Czech word order is flexible, but the original sentence is very natural.

You could also say:

• Napíšu seznam, než půjdu do obchodu.

That still means roughly I’ll write a list before I go to the shop, although many speakers may prefer the original order because it sets up the time frame first.

The original version:

• Než půjdu do obchodu, napíšu seznam...

sounds smooth and clear:

1. first, it says before I go to the shop
2. then, it says what happens first: I’ll write a list

So yes, the order can change, but the given sentence is a very natural way to say it.