Learn Hardcore Czech: V galerii jsme navštívili novou sbírku obrazů, které visí jen jeden týden. - In the gallery we visited a new collection of paintings that will hang there for only one week.

In 1st and 2nd person, the auxiliary (jsem, jsi, jsme, jste) is always used in standard Czech.
In 3rd person, the auxiliary is often dropped in speech (e.g. navštívili vs. oni navštívili).

What is the difference between navštívit and navštěvovat?

This is about aspect, a big feature of Czech verbs.

navštívit – perfective: one completed visit, a single event
- V galerii jsme navštívili… = We visited (once, completed).
navštěvovat – imperfective: repeated or habitual action
- Navštěvujeme galerii každý měsíc. = We visit the gallery every month.

In your sentence the visit is a single, finished event, so navštívit is correct.

Why is it novou sbírku and not nová sbírka?

Sbírka (collection) is feminine:

nominative: nová sbírka – “a new collection” (subject)
accusative: novou sbírku – “(we visited) a new collection” (direct object)

In the sentence, novou sbírku is what we visited, so it is in the accusative case (direct object of navštívili).

Hence:
V galerii jsme navštívili novou sbírku…
= We visited a new collection…

Why is it sbírku obrazů and not sbírku obrazy?

After sbírka (collection), Czech normally uses the genitive to say “collection of X”:

sbírka známek – a collection of stamps
sbírka knih – a collection of books
sbírka obrazů – a collection of paintings

So obrazů is genitive plural of obraz (painting):

nominative plural: obrazy (paintings)
genitive plural: obrazů (of paintings)

Using sbírku obrazy would be wrong; we need the “of” relation, so genitive obrazů.

Why is the relative pronoun které and not která?

The pronoun must agree with the noun it refers to in gender and number.

We have:

sbírka = collection – feminine singular
obrazů = of paintings – underlying plural obrazy, masculine inanimate plural

The relative clause které visí jen jeden týden logically describes the paintings (they are what hang), not the collection. So the pronoun agrees with obrazy:

obrazy, které visí… – paintings that hang…
nominative plural relative pronoun: které

If it described sbírka, it would be:

sbírka, která trvá jen jeden týden. – a collection/exhibition that lasts only one week.

So které is plural (matching obrazy), not singular feminine která.

Does které visí jen jeden týden describe the collection or the paintings?

Grammatically and logically, it describes the paintings:

the collection is sbírka (feminine singular)
the paintings are obrazy (implied by obrazů, genitive plural)
the pronoun které is plural and matches obrazy

Also, you normally say that paintings hang, not that a collection hangs.

So the meaning is:

“…a new collection of paintings that hang only for one week.”

Why is visí in the present tense here?

Visí is the present tense of viset (to hang).

Czech uses the present tense:

For a current ongoing state:
- Obrazy visí v galerii. – The paintings are (currently) hanging in the gallery.
For a temporary but current situation:
- …obrazy, které visí jen jeden týden.
  = paintings that are only up for one week.

English might suggest a future idea (“will be there for only one week”), but Czech can still use the present tense to describe the time-limited state that is happening now.

What exactly does jen mean, and could we use pouze or jenom?

Jen means “only” / “just” in this context.

jen jeden týden = only one week

You can usually replace jen with:

jenom – a bit more colloquial, but very common: jenom jeden týden
pouze – more formal: pouze jeden týden

All three work here; the nuance is mostly style:

jen / jenom – neutral, everyday
pouze – more formal, written, or “official” tone

Why is it jen jeden týden and not simply jen týden?

Both are possible:

jen týden – only a week
jen jeden týden – only one week (a little more emphatic that it is exactly one)

Adding jeden emphasizes the exact number. In many contexts, you can drop jeden:

Byl tam jen týden. – He was there only a week.
Byl tam jen jeden týden. – He was there only one week (and that’s surprisingly short, for example).

In your sentence, jen jeden týden underlines that the display time is strictly one week.

Why is there a comma before které?

The comma marks the beginning of a relative clause (a subordinate clause giving extra information about a noun).

Main clause: V galerii jsme navštívili novou sbírku obrazů
Relative clause: které visí jen jeden týden

Czech, like English, normally separates such clauses with a comma:

“We visited a new collection of paintings, which hang only for one week.”

Why is there no my (we) in the sentence? Can it be added?

Czech is a pro‑drop language: subject pronouns are often omitted because the person is already clear from the verb form.

jsme navštívili can only mean we visited, so my is not needed.

You can add my for emphasis or contrast:

My jsme navštívili novou sbírku…
– We visited the new collection (as opposed to someone else).

But the neutral, natural version usually omits my:

V galerii jsme navštívili…

Could we change the word order, for example: Navštívili jsme v galerii novou sbírku obrazů…?

Yes, Czech word order is quite flexible, but it affects emphasis and naturalness.

Some options:

V galerii jsme navštívili novou sbírku obrazů…
– neutral, first sets the scene “in the gallery”.
Navštívili jsme v galerii novou sbírku obrazů…
– possible, but v galerii sounds more like inserted extra info.
Navštívili jsme novou sbírku obrazů v galerii.
– also possible; v galerii now directly modifies novou sbírku obrazů.

The original order is very natural because it starts with the place (topic) and then says what happened there.

If I want to say the exhibition lasts only one week (not the paintings “hang” one week), how could I rephrase the sentence?

You would then refer to the exhibition / event, not the physical hanging of paintings. For example:

V galerii jsme navštívili novou výstavu obrazů, která trvá jen jeden týden.
= In the gallery we visited a new exhibition of paintings that lasts only one week.

V galerii jsme navštívili novou výstavu obrazů, která je k vidění jen jeden týden.
= …which is on display for only one week.

Here the relative pronoun is která (singular feminine), because it refers to výstava (exhibition), not to obrazy (paintings).