אם יהיה מקום בצידנית, נשים גם שזיפים וגם קצת אבטיח.

Because Hebrew commonly uses the future tense after אם when the condition is about the future.

So:

• אם יהיה מקום = literally if there will be room
• natural English = if there is room

This is a very common difference between the two languages. In Hebrew, both parts of the sentence can be future:

• אם יהיה מקום..., נשים...
• If there is room..., we’ll put...

So the Hebrew tense is normal here, even if English uses a present form.

Because the subject is מקום, and מקום is a masculine singular noun.

• מקום = masculine singular
• therefore: יהיה

The word צידנית is feminine, but it is not the subject. It is just part of the phrase בצידנית = in the cooler.

So the agreement is with מקום, not with צידנית.

יש means there is / there are in the present.

For future existence, Hebrew uses forms of להיות:

• יש מקום = there is room
• יהיה מקום = there will be room

Since the sentence is talking about a future possibility, יהיה is the right choice.

It is the preposition ב־ (in) attached to צידנית (cooler / ice chest).

So:

• ב + צידנית → בצידנית

One useful thing to know: in normal unpointed Hebrew writing, בצידנית can mean either:

• in a cooler
• in the cooler

The difference is usually only visible with vowel marks, which are normally omitted. So context tells you which one is meant.

מקום can mean both place and space/room, depending on context.

Here, because we are talking about fitting food into a cooler, מקום clearly means:

• space
• room

So אם יהיה מקום בצידנית means if there’s room in the cooler, not if there’s a place in the cooler in the location sense.

Yes, it can be either:

• נשים = women (noun)
• נשים = we will put (verb, from לשים)

Context tells you which one it is.

Here it is clearly a verb because it comes after the condition and is followed by objects:

• נשים גם שזיפים וגם קצת אבטיח
• we’ll put in both plums and a little watermelon

So this נשים is we will put.

Because Hebrew verbs already show the person and number.

• נשים already means we will put

So אנחנו is not necessary. Hebrew often leaves subject pronouns out unless they are needed for emphasis or contrast.

You could say:

• אם יהיה מקום בצידנית, אנחנו נשים גם שזיפים וגם קצת אבטיח

But the version without אנחנו is more natural unless you want emphasis.

This structure means both ... and ... or also ... and also ....

So:

• גם שזיפים וגם קצת אבטיח = both plums and a little watermelon

A single גם often just means also, but when you get גם ... וגם, it links two things together and emphasizes that both are included.

Because את is used before definite direct objects, and these objects are indefinite.

Here we have:

• שזיפים = plums, not the plums
• קצת אבטיח = a little watermelon / some watermelon, not the watermelon

So no את appears.

Compare:

• נשים שזיפים = we’ll put plums
• נשים את השזיפים = we’ll put the plums

Because אבטיח here is being treated like a mass noun, similar to English some watermelon.

So:

• קצת אבטיח = a little watermelon / some watermelon

It does not have to mean a whole watermelon. It usually means some amount of watermelon, such as pieces or slices.

If you wanted to be more specific, Hebrew could also say things like:

• קצת מהאבטיח = a little of the watermelon
• חתיכת אבטיח = a piece of watermelon

But קצת אבטיח is very natural.

Yes. Hebrew can also put the main clause first:

• נשים גם שזיפים וגם קצת אבטיח, אם יהיה מקום בצידנית

But the version with the אם clause first is very natural and common.

When the condition comes first, the comma is standard:

• אם יהיה מקום בצידנית, נשים...

That structure is very similar to English: If there’s room in the cooler, we’ll put...

It is a very common verb, but its future forms are a little irregular-looking for learners.

The future forms are:

• אשים = I will put
• תשים = you will put / she will put
• ישים = he will put
• נשים = we will put
• תשימו = you all will put
• ישימו = they will put

So נשים is simply the normal future we form of לשים.

Then Hebrew would normally use the article ה־ and also the direct-object marker את:

• אם יהיה מקום בצידנית, נשים גם את השזיפים וגם את האבטיח.

That means:

• If there is room in the cooler, we’ll put in both the plums and the watermelon.

So the original sentence sounds more like some plums and some watermelon, not specific previously mentioned items.