watasi ha suupaa de ringo wo mittu kaimasita.

In this sentence, は is the topic particle, and when は is used as a particle, it is pronounced wa, not ha.

So:

• 私 = I / me
• は = marks 私 as the topic of the sentence

That is why 私は is read watashi wa.

This is a very common beginner question because the written form and the pronunciation do not match here.

は marks the topic of the sentence.

In 私はスーパーでりんごを三つ買いました, the topic is 私 (I / as for me).

A natural way to think of it is:

• As for me, I bought three apples at the supermarket.

English does not usually mark the topic separately, so this can feel unfamiliar at first.

Also, learners often wonder why it is not が. In a simple sentence like this, は is used because the speaker is talking about themselves as the topic. が would give a different nuance, often focusing more directly on the subject.

で marks the place where an action happens.

Here, the action is 買いました (bought), and that action happened at the supermarket.

So:

• スーパーで = at the supermarket

This is different from particles like:

• に for destination or existence in some cases
• へ for direction
• で for the location of an action

Because buying is an action done at a place, で is the correct particle here.

を marks the direct object of the verb, meaning the thing directly affected by the action.

In this sentence:

• りんご = apples
• を = marks apples as the thing that was bought

So:

• りんごを買いました = bought apples

In other words, を tells you what was bought.

Japanese usually uses a counter when counting things.

三つ means three things and uses the general counter series:

• 一つ
• 二つ
• 三つ
• 四つ
• etc.

For apples, using 三つ is very natural because apples are countable objects and the -つ counter works well for many everyday items.

If you said just 三, it would sound incomplete, because Japanese normally wants a number plus a counter.

Yes, 三個 is also possible.

Both can work for apples:

• 三つ = three items, using a general native Japanese counter
• 三個 = three pieces/items, using 個, a very common counter for small-ish concrete objects

For apples, 三つ sounds very natural and basic, especially in beginner material.
三個 is also natural in real life.

A rough difference:

• 三つ can sound a little more general and simple
• 三個 sounds a little more specifically like counting physical units

For a beginner, it is best to understand that both are possible, but 三つ is extremely common and easy to learn early on.

In Japanese, quantity expressions often come after the object they count.

So this pattern is very common:

• りんごを三つ買いました
• literally: apples three bought

This sounds strange in English, but it is normal in Japanese.

You may also see other word orders in some contexts, but object + を + quantity + verb is a very standard pattern.

So here:

• りんごを = apples
• 三つ = three
• 買いました = bought

Together: bought three apples

Japanese sentences usually place the main verb at the end.

That is one of the biggest differences from English.

English:

• I bought three apples at the supermarket.

Japanese:

• I / supermarket at / apples / three / bought

So in Japanese, the verb comes last:

• 買いました

This final position helps signal that the sentence is complete.

The dictionary form is 買う (kau) = to buy.

買いました is the polite past form.

Breakdown:

• 買う = buy
• 買い = verb stem
• ました = polite past ending

So:

• 買いました = bought

If you wanted the plain past form, it would be:

• 買った = bought

ました is the polite past ending for verbs.

It shows two things:

1. Past tense
   The action already happened.

2. Politeness
   The speaker is using a polite style.

So 買いました means bought in a polite way.

Compare:

• 買った = bought, plain/casual
• 買いました = bought, polite

This is the kind of form you would use in class, with strangers, with coworkers, or in most polite everyday situations.

Yes, very often.

Japanese frequently leaves out words that are clear from context. If it is already obvious that the speaker is talking about themselves, you can simply say:

• スーパーでりんごを三つ買いました。

This still naturally means I bought three apples at the supermarket, depending on context.

Beginners often see 私 included more often than native speakers would use it in conversation, because textbooks like to make the sentence structure clear.

No, not in ordinary Japanese writing.

The sentence is normally written like this:

私はスーパーでりんごを三つ買いました。

Spaces are often added in beginner materials to make the parts easier to see, but standard Japanese usually does not put spaces between words.

So the spaced version is just for learning.

スーパー is a loanword, borrowed from English supermarket (or more specifically from the shortened Japanese form of it).

Katakana is commonly used for:

• foreign loanwords
• foreign names
• some sound effects
• emphasis in certain cases

So:

• スーパー = supermarket

This is a very normal use of katakana.