ليست معنا البطانية فقط، بل القبعة والكرة أيضا.

Because Arabic is not using a verb to have here.

The structure is literally closer to the blanket is not only with us than to we do not only have the blanket.

So:

• معنا = with us
• البطانية = the thing being talked about
• ليست agrees with البطانية, not with نا

That is why you get ليست and not لسنا.

معنا is made of:

• مع = with
• نا = us

So معنا literally means with us.

In Arabic, expressions with مع or عند are often used where English would use have. So in context, معنا البطانية can mean we have the blanket with us.

Because البطانية is a feminine singular noun.

Arabic past-tense verbs and words like ليس often agree with the subject in gender and number. Here the relevant noun is البطانية, so the form is:

• ليست = feminine singular
• not ليس = masculine singular

So the sentence is structured around the blanket, which is feminine.

Both orders are possible in Arabic.

This sentence puts معنا early:

• ليست معنا البطانية فقط

That sounds natural because Arabic often places the predicate or prepositional phrase early, especially in this kind of statement.

Compare:

• البطانية ليست معنا فقط
• ليست معنا البطانية فقط

Both are understandable, but the given order is very natural in formal Arabic.

Because فقط usually comes after the word or phrase it limits.

So:

• البطانية فقط = the blanket only / only the blanket

In this sentence, فقط tells you that the first item being singled out is the blanket.

Arabic often places only after the focused element rather than before it, unlike English.

Together, they create the idea of not only ..., but also ...

So:

• بل = rather / but rather / but
• أيضا = also

In this pattern:

• ليست معنا البطانية فقط، بل القبعة والكرة أيضا

the meaning is:

• not only the blanket ..., but also the hat and the ball

A very common Arabic pattern is:

• ليس/ليست ... فقط، بل ... أيضًا

Because Arabic often omits repeated words when they are easy to understand from context.

So after:

• بل القبعة والكرة أيضا

the listener understands something like:

• بل القبعة والكرة أيضا معنا or
• بل القبعة والكرة أيضا ليست معنا فقط? No—here the understood meaning is simply the hat and the ball are with us too

A fuller version could be:

• ليست معنا البطانية فقط، بل القبعة والكرة معنا أيضا

But Arabic often prefers the shorter version.

It applies to the whole phrase القبعة والكرة.

Even though أيضا comes at the end, its meaning is broader:

• the hat and the ball also

So it does not mean that only the ball is also included. It adds the entire coordinated phrase.

Because they are definite nouns:

• البطانية = the blanket
• القبعة = the hat
• الكرة = the ball

This suggests specific, known items, not just any blanket, hat, or ball.

If the nouns were indefinite, the meaning would shift:

• بطانية = a blanket
• قبعة = a hat
• كرة = a ball

So the الـ matches the idea of specific objects.

A useful analysis is:

• ليست = negative copular verb, like is not
• معنا = a prepositional phrase functioning as the predicate
• البطانية = the subject of ليس
• فقط = only
• بل = but rather / but
• القبعة والكرة = the added items in the parallel second part
• أيضا = also

If full case endings were written, you would normally have:

• البطانيةُ
• القبعةُ
• الكرةُ

In normal Arabic writing, those endings are usually not shown.

Yes. For example:

• ليست البطانية معنا فقط، بل القبعة والكرة أيضا.
• ليست معنا البطانية وحدها، بل القبعة والكرة أيضا.

These are very close in meaning.

The original sentence is perfectly good Arabic, and it uses a common formal pattern for not only ..., but also ....