pan ya kudamono wo hanbun dake tumetara, kaban ni zenbu haitta.

Not exactly.

• や means something like ...and..., among other things or ...such as...
• と gives a more complete, closed list: A and B
• や gives a looser, more representative list: A, B, and the like

So パンや果物 suggests bread, fruit, and possibly other similar things. It does not sound as exact as パンと果物.

Because パンや果物 is the direct object of 詰めた.

• 詰める is a transitive verb here: you pack something
• The thing being packed takes を

So:

• パンや果物を詰める = to pack bread, fruit, etc.

半分 means half, and だけ means only.

Together, 半分だけ means only half.

In this sentence, it means that only half of the amount under discussion was packed. In natural English, this is often understood as:

• only half of the bread and fruit
• or only half as much of those things

It does not usually mean I packed them halfway. It means the amount packed was half.

By itself, it is a little flexible. It usually means half of the relevant amount, based on context.

So this sentence could mean:

• half of the bread and fruit overall
• or roughly half of what was originally going to be packed

If you wanted to make half of each very explicit, you could say something like:

• パンと果物をそれぞれ半分だけ

That それぞれ makes the each idea clearer.

たら is a conditional form made from the past tense form of a verb.

• 詰めた = packed
• 詰めたら = if/when/after packing

In this sentence, たら connects the first action to the result in the second clause:

• When/After I packed only half, everything fit in the bag
• or If I packed only half, everything fit

Because the second clause describes an actual result, when/after is often the most natural interpretation here.

Both can relate to putting things into something, but the nuance is different.

• 入れる = to put in
• 詰める = to pack, stuff, or fill

With bags, boxes, or suitcases, 詰める often sounds more like packing things in, especially when several items are involved.

So:

• かばんに物を入れる = put things in a bag
• かばんに物を詰める = pack things into a bag

Here, 詰める matches the idea of packing a bag better.

Because 入る is an intransitive verb.

• 入る = to enter, to go in, to fit
• Intransitive verbs do not take a direct object with を in the normal way

With 入る, the container or destination is marked by に:

• かばんに入る = to go into / fit in the bag

So かばんに全部入った is correct.

If you used the transitive verb 入れる, then you could say:

• 全部をかばんに入れた = I put everything into the bag

The subject is omitted, which is very common in Japanese.

Here, 全部 means all of it / everything, and it refers to the things being talked about in context, probably the items that were packed.

So the idea is:

• all of it fit in the bag
• or everything went into the bag

Japanese often leaves this kind of subject unstated when it is clear from context.

You can think of the sentence as having an understood subject like:

• それが全部入った
• 荷物が全部入った

But in natural Japanese, leaving it out is normal.

Because 全部 can work in an adverb-like way in sentences like this.

So 全部入った is a very natural way to say:

• it all fit
• everything fit

If you want to mark it more explicitly as the subject, you could say:

• 全部が入った

Both are possible, but 全部入った sounds very natural in everyday Japanese.

Because the sentence describes a completed result.

The sequence is:

1. only half was packed
2. as a result, everything fit in the bag

So 入った is past because the fitting-in already happened.

Japanese often uses past tense this way to report the outcome of an action:

• やってみたら、うまくいった
• When I tried it, it worked

This sentence has the same kind of flow.

The person doing the packing is understood from context, and Japanese very often omits subjects that are obvious.

So the first clause naturally implies something like:

• I packed only half
• or we packed only half

Japanese does not need to say 私は unless there is a reason to emphasize or contrast the subject.

That means the sentence can smoothly move from:

• an implied human doer in 詰めたら to
• the packed items as the understood subject of 入った

This kind of subject shift is completely normal in Japanese.

Japanese nouns usually do not mark singular vs. plural the way English does.

So:

• パン can mean bread or breads, depending on context
• 果物 can mean fruit or fruits

Japanese often leaves number unspecified unless it matters.

That is why there is no extra plural marking here. The context tells you whether the speaker means a general amount of bread and fruit, several items, or a collection of food.

Yes. Japanese often leaves things implicit, but you could make parts clearer.

For example:

• パンや果物を半分だけかばんに詰めたら、全部入った。
• パンや果物を半分だけ詰めたら、それが全部かばんに入った。

These are more explicit about what went into the bag.

Still, the original sentence is very natural. It relies on context in a way that Japanese often does.