pan to tiizu dake nara, naihu ga nakute mo daizyoubu desu.

It means if it’s just bread and cheese or as long as it’s only bread and cheese.

Breakdown:

• パン = bread
• と = and
• チーズ = cheese
• だけ = only, just
• なら = if, when it comes to, as for

So the speaker is setting up a condition: if we’re talking about only bread and cheese...

と is the normal particle for connecting nouns and means and.

So:

• パンとチーズ = bread and cheese

This is different from using と to mean with in some other sentences. Here it is simply joining two nouns in a list.

なら introduces a condition, but it often has the nuance of if that’s the case or if we’re talking about that.

So:

• パンとチーズだけなら = if it’s just bread and cheese
• It sounds like the speaker is responding to a situation or assumption already on the table.

Compared with たら:

• たら is often a more neutral if/when
• なら can feel more like given that or in that case

Here, なら fits well because the sentence sounds like:
If it’s only bread and cheese, then a knife isn’t necessary.

なくても means even if there isn’t... or without...

It comes from ない:

• ある = to exist / to have
• ない = not exist / not have
• なくて = te-form of ない
• なくても = even if not / even without

So:

• ナイフがない = there is no knife / you don’t have a knife
• ナイフがなくても = even if there is no knife / without a knife

In natural English here, without a knife is the best translation.

Because with ある / ない, the thing that exists or does not exist is commonly marked by が.

So:

• ナイフがある = there is a knife
• ナイフがない = there is no knife

That is why the sentence uses:

• ナイフがなくても = even without a knife

Could は appear instead? Yes, but it would add contrast or emphasis:

• ナイフはなくても大丈夫です = as for a knife, it’s okay even without one

The version with が is more neutral.

Here, 大丈夫です means it’s fine, it’s okay, or no problem.

It does not mean safe in a literal physical-safety sense here.
The idea is:

• A knife is not necessary
• You’ll be fine without one

So the sentence is saying that for bread and cheese, not having a knife is not a problem.

Yes, Japanese often leaves out things that are obvious from context.

This sentence does not explicitly say:

• who is eating
• what exactly will be done
• why it is okay

English often wants something more explicit, like:

• If it’s just bread and cheese, you’ll be fine without a knife.
• If it’s only bread and cheese, you don’t need a knife.

In Japanese, that extra information can be omitted if the meaning is clear.

The comma marks a pause after the conditional phrase:

• パンとチーズだけなら、

It helps separate the if... part from the main statement:

• If it’s just bread and cheese, ...
• ... it’s okay even without a knife.

In Japanese, commas are often used more flexibly than in English. This comma is natural, but punctuation can vary depending on style.

Yes. A few natural alternatives are possible, for example:

• パンとチーズだけなら、ナイフはなくても大丈夫です。
  Slightly more contrast on knife

• パンとチーズだけなら、ナイフがなくても平気です。
  平気です is similar to 大丈夫です

• パンとチーズだけなら、ナイフはいりません。
  This means If it’s just bread and cheese, you don’t need a knife

The original sentence is very natural and polite.

They are almost certainly just for learners.

Normally, Japanese is written without spaces:

• パンとチーズだけなら、ナイフがなくても大丈夫です。

Textbooks and learning materials often insert spaces to make the structure easier to see. In real Japanese writing, you usually would not see them.