Demà vull penjar un altre quadre a la paret del passadís.

Yes. Demà means tomorrow, and Catalan often puts time expressions at the beginning of the sentence for emphasis or simply because it sounds natural:

• Demà vull penjar un altre quadre...
• Vull penjar un altre quadre demà...

Both are correct. Starting with Demà highlights when the action will happen.

It means I want to hang.

Catalan uses the structure:

• vull = I want
• penjar = to hang

So vull penjar literally matches the idea I want to hang.

This is a very common pattern:

• Vull menjar = I want to eat
• Vull marxar = I want to leave
• Vull comprar-lo = I want to buy it

Unlike English, Catalan does not need a separate word exactly like to between want and the second verb.

Here, penjar means to hang up or to put up something, such as a picture on a wall.

Common uses of penjar include:

• penjar un quadre = to hang a picture
• penjar l’abric = to hang up the coat
• penjar el telèfon = to hang up the phone

So in this sentence, it clearly refers to physically hanging a picture on the wall.

Because altre usually goes with an article or determiner.

So:

• un altre quadre = another picture
• l’altre quadre = the other picture

Using altre by itself is generally not the normal choice here.

For an English speaker, it helps to think:

• un altre = another
• l’altre = the other

Quadre often means picture, painting, or framed picture, especially something you hang on a wall.

Depending on context, it can also mean:

• a painting
• a framed artwork
• sometimes even a chart/table in other contexts

In this sentence, because it is being hung on a wall, quadre is best understood as picture or painting.

Here a means something like on in English.

So:

• a la paret = on the wall

This is one of those places where Catalan and English use different prepositions. English says on the wall, but Catalan normally says a la paret.

You should learn it as a fixed expression:

• penjar un quadre a la paret = to hang a picture on the wall

Del is a contraction of:

• de + el = del

So:

• el passadís = the hallway
• de el passadís becomes del passadís = of the hallway

Therefore:

• la paret del passadís = the wall of the hallway / more naturally in English, the hallway wall

This kind of contraction is very common in Catalan.

Catalan often expresses this idea with noun + de + noun:

• la porta de casa = the house door / the front door
• la finestra de l’habitació = the bedroom window
• la paret del passadís = the hallway wall

English often uses a noun directly before another noun, but Catalan usually prefers a structure with de.

The written accents show where the stress falls.

• Demà: stress on the last syllable → de-MÀ
• passadís: stress on the last syllable → pas-sa-DÍS

The accents are important because they tell you which syllable to emphasize.

Yes. That would also be correct, but it means something slightly different in structure.

• Demà vull penjar un altre quadre... = Tomorrow I want to hang another picture...
• Demà penjaré un altre quadre... = Tomorrow I will hang another picture...

The first talks about wanting/intending to do it. The second talks more directly about doing it in the future.

Because Catalan often drops subject pronouns when the verb already makes the subject clear.

• vull already means I want

So jo is not necessary:

• (Jo) vull penjar un altre quadre...

Including jo is possible, but usually only for emphasis or contrast:

• Jo vull penjar-lo demà, no avui. = I want to hang it tomorrow, not today.

Not completely. Catalan allows some flexibility, although some orders sound more natural than others.

Natural versions include:

• Demà vull penjar un altre quadre a la paret del passadís.
• Vull penjar un altre quadre a la paret del passadís demà.

But the original is very natural because it goes:

1. time
2. verb of wanting
3. action
4. object
5. place

That makes it easy to follow.