Dijous el teló s'obrirà a les vuit, i divendres hi tornarà la mateixa orquestra.

In Catalan, days of the week can be used without a preposition to mean on Thursday / on Friday in many contexts, especially in schedules, announcements, and narrative style.

So:

• Dijous = on Thursday / Thursday
• divendres = on Friday / Friday

You may also see:

• el dijous = on Thursday or Thursdays, depending on context
• els dijous = on Thursdays / every Thursday

In this sentence, Dijous ... i divendres ... sounds natural and concise, like a program note or event announcement.

El teló means the curtain, especially the theater stage curtain.

So in this context, it is not just any fabric curtain in a house, but specifically the curtain in a performance venue.

Related words:

• teatre = theater
• escenari = stage
• teló = stage curtain

S'obrirà comes from obrir-se, literally to open itself, and here it is used in a way that corresponds to English will open.

So:

• obrir = to open something
• obrir-se = to open

Examples:

• Obriran la porta. = They will open the door.
• La porta s'obrirà. = The door will open.

In your sentence:

• el teló s'obrirà = the curtain will open

This is very natural in Catalan for things that open, close, break, move, etc.

The s' is the clitic pronoun es, shortened before a vowel.

So:

• es obrirà becomes s'obrirà

Catalan often shortens pronouns this way:

• se + obre → s'obre
• es + aixeca → s'aixeca

It is just the normal written contraction before a vowel sound.

Catalan uses a before clock times:

• a la una = at one
• a les dues = at two
• a les vuit = at eight

So:

• el teló s'obrirà a les vuit = the curtain will open at eight

Notice:

• la una is singular
• most other hours use les

Here hi means there.

So:

• tornar-hi = to return there / to go back there

In the sentence:

• divendres hi tornarà la mateixa orquestra = on Friday the same orchestra will return there

The there refers to the place already understood from context, probably the theater or venue.

Catalan often uses hi where English might use:

• there
• to it
• in it
• at that place

Yes, you could say divendres tornarà la mateixa orquestra, but it would usually mean simply the same orchestra will return / come back on Friday, without explicitly marking the place.

Adding hi makes the destination or location clear:

• tornar = return, come back
• tornar-hi = return there

So hi adds the idea of back to that place.

Catalan often allows the subject to come after the verb, especially in announcements, narrative, and when introducing or highlighting the action first.

So both are possible in many contexts:

• La mateixa orquestra hi tornarà divendres.
• Divendres hi tornarà la mateixa orquestra.

The version in your sentence sounds quite natural and stylistically smooth, especially in program-like language. It puts focus first on:

1. the day
2. the action of returning
3. who returns

La mateixa orquestra means the same orchestra.

The adjective mateix / mateixa / mateixos / mateixes means same.

Agreement:

• el mateix concert = the same concert
• la mateixa orquestra = the same orchestra
• els mateixos músics = the same musicians
• les mateixes obres = the same works/pieces

So mateixa is feminine singular because orquestra is feminine singular.

Catalan usually uses mateix for the same, while igual more often means equal, identical, or similar/same in quality depending on context.

So:

• la mateixa orquestra = the same orchestra (the very same one)
• una orquestra igual = a similar / identical orchestra, not necessarily the exact same one

For identity, mateix is the normal choice here.

They are in the simple future.

Forms:

• obrirà = will open
• tornarà = will return

Infinitives:

• obrir
• tornar

The ending -à here is the third person singular future:

• jo obriré
• tu obriràs

• ell/ella obrirà

• jo tornaré
• tu tornaràs
• ell/ella tornarà

So:

• el teló s'obrirà = the curtain will open
• la mateixa orquestra hi tornarà = the same orchestra will return there

I means and.

It links the two parts of the sentence:

• Dijous el teló s'obrirà a les vuit
• i divendres hi tornarà la mateixa orquestra

So the sentence is simply coordinating two events:

1. what happens Thursday
2. what happens Friday

Yes. The sentence has a slightly formal, program-like style, the kind you might see in:

• a theater brochure
• an event schedule
• a cultural announcement
• a newspaper listing

Features that create that effect:

• starting with the day name: Dijous, divendres
• concise future forms: s'obrirà, tornarà
• use of hi to avoid repeating the venue
• postverbal subject: hi tornarà la mateixa orquestra

So although the grammar is normal, the sentence sounds polished and idiomatic rather than conversationally casual.