suupaa de pointokaado wo dasitara, tamago ga sukosi yasuku narimasita.

で marks the place where an action happens.

• スーパーで = at the supermarket
• The action here is ポイントカードを出した = showed/took out the point card

So スーパーで tells you where that action happened.

Compare:

• スーパーで買いました = I bought it at the supermarket
• スーパーに行きました = I went to the supermarket

Use で for the location of an action, and に for destination/existence in many cases.

を marks the direct object of the verb.

Here, the verb is 出す, which in this context means to take out / present / show.
So:

• ポイントカードを出す = to show/present a point card

The thing being presented is ポイントカード, so it takes を.

Yes, literally 出す often means to take out / bring out / put out, but in real-life situations it often means to present/show something.

In this sentence:

• ポイントカードを出したら means something like
  when I showed my point card
  or
  after I presented my point card

This is a very common use:

• 財布を出す = take out your wallet
• チケットを出す = show your ticket
• 保険証を出す = present your insurance card

The ～たら form can mean either if or when, depending on context.

Here, the sentence describes something that actually happened in the past:

• ポイントカードを出したら、卵が少し安くなりました。

So ～たら is naturally understood as when/after I did that rather than a hypothetical if.

A helpful way to think of it here is:

• 出したら = when I showed it / after I showed it

Because the second part describes the result that actually occurred:

• 卵が少し安くなりました = the eggs became a little cheaper

Because 卵 is not the direct object of the verb なる.

The verb here is:

• 安くなる = to become cheap / cheaper

With なる, the thing that changes is often marked by が.

So:

• 卵が安くなりました = The eggs became cheaper

Compare:

• 卵を買いました = I bought eggs
  → 卵 is the direct object, so を
• 卵が安くなりました = eggs became cheaper
  → 卵 is the thing undergoing the change, so が

It is built like this:

• 安い = cheap
• 安く = the adverb/connecting form of 安い
• なる = to become

So:

• 安い → 安くなる = to become cheap / cheaper

Then in polite past:

• 安くなりました = became cheaper

This pattern is very common with い-adjectives:

• 高い → 高くなる = become expensive
• 早い → 早くなる = become early/faster
• 寒い → 寒くなる = become cold

Because the verb is なる, which means to become.

So:

• 安いです = it is cheap
• 安くなりました = it became cheaper

This suggests a change in price, not just a description of the usual price. In this sentence, the change happened because the point card was presented.

少し means a little or slightly.

So:

• 卵が少し安くなりました = the eggs became a little cheaper

It softens the statement and shows the discount was small.

Similar words:

• 少し = a little
• ちょっと = a little, a bit more casual
• かなり = quite, fairly
• とても = very

Japanese often leaves out subjects when they are clear from context.

So in:

• ポイントカードを出したら

the understood subject is probably I, because the speaker is describing what happened when they showed the card.

A natural fuller version could be:

• スーパーで私がポイントカードを出したら、卵が少し安くなりました。

But 私が is usually unnecessary unless you want emphasis or contrast. Japanese prefers omission when the meaning is clear.

It could be either, depending on context.

Japanese nouns usually do not change form for singular vs. plural. So:

• 卵 can mean egg or eggs

In this sentence, English will usually translate it as eggs, because supermarket pricing often refers to eggs as a product/item. But Japanese itself does not force that distinction here.

Because it uses the polite past form なりました.

The plain version would be:

• スーパーでポイントカードを出したら、卵が少し安くなった。

The polite version:

• スーパーでポイントカードを出したら、卵が少し安くなりました。

Japanese often uses polite forms in ordinary conversation, especially when speaking to someone you are not very close to, or just to sound more neutral and respectful.

Sometimes, but the nuance changes.

1. ～たら

   • ポイントカードを出したら、卵が少し安くなりました。
   • Natural for when/after I did that, this happened

2. ～て

   • ポイントカードを出して、卵が少し安くなりました。
   • This sounds less natural here, because て often just connects actions, and it can sound like I showed the card, and then the eggs became cheaper, without clearly highlighting the conditional/result relationship.

3. ～と

   • ポイントカードを出すと、卵が少し安くなります。
   • This sounds more like a general rule: when you show your point card, the eggs get a little cheaper

So ～たら is a very good choice when talking about a specific past event and its result.

Yes. ポイントカード is a common Japanese term for a store loyalty card or reward card.

So this sentence implies:

• the store has a point-card system
• presenting that card affected the price or applied some benefit

In everyday Japanese, ポイントカードを出す is a very normal expression at shops, restaurants, and pharmacies.

Japanese often describes the result from the item’s point of view:

• 卵が少し安くなりました = the eggs became a little cheaper

This is very natural in Japanese. English often prefers a more agent-based expression, such as:

• I got a small discount on the eggs
• The eggs were a little cheaper

Japanese frequently uses X が ～くなる to describe a change in state, even when English might phrase it differently.