kono pasokon ha hurui desu ga, mada tukaemasu.

この means this, but it is a determiner, not a standalone pronoun. That means it must come before a noun.

• この パソコン = this computer
• You cannot normally say just この to mean this one

If you want to say this one, you would use これ instead.

• これは古いです。 = This one is old.
• このパソコンは古いです。 = This computer is old.

In this sentence, は is the topic particle, and when は is used as a particle, it is pronounced wa.

So:

• この パソコン は is pronounced kono pasokon wa

This is one of the first special pronunciation rules learners meet in Japanese. The spelling stays は, but the pronunciation changes when it functions as a particle.

は marks the topic of the sentence. It tells you what the sentence is about.

So:

• このパソコンは = As for this computer, ...

The rest of the sentence gives information about that topic:

• 古いですが、まだ使えます。
• It is old, but it can still be used.

A literal breakdown would be something like:

• As for this computer, it is old, but it is still usable.

古い is an い-adjective. With い-adjectives, you do not use だ after them.

Correct:

• 古いです = polite
• 古い = plain

Incorrect:

• 古いだ

This is different from noun and な-adjective sentences, where だ or です can appear:

• 学生だ / 学生です
• 静かだ / 静かです

But with い-adjectives:

• 古い
• 古いです

So in this sentence, です just adds politeness.

Not exactly. In beginner translations, 古いです is often translated as is old, but grammatically 古い already carries the meaning old as the predicate.

So:

• 古い = is old / old
• 古いです = the polite version of that

In other words, です here mainly adds politeness, rather than working exactly like English is.

Here, が means but.

So:

• 古いですが = it is old, but...

This が connects two ideas:

1. the computer is old
2. it is still usable

A very natural English translation is:

• This computer is old, but you can still use it.

Do not confuse this with the other が, the subject marker. In this sentence, が is a conjunction meaning but.

Yes, けど or けれども could also be used.

Examples:

• このパソコンは古いですが、まだ使えます。
• このパソコンは古いけど、まだ使えます。

The difference is mostly one of tone:

• が is a bit more formal or written-sounding
• けど is more conversational
• けれども can sound a little more formal or fuller

Since the sentence uses です / ます polite style, ですが fits nicely.

Here, まだ means still.

So:

• まだ使えます = can still be used

This shows that even though the computer is old, the condition continues: it remains usable.

A very common learner confusion is that まだ can also appear in negative sentences to mean not yet:

• まだ食べていません。 = I haven’t eaten yet.

So まだ does not always mean the same thing in English. Its meaning depends on the sentence:

• with a positive verb: often still
• with a negative verb: often not yet

使えます is the polite potential form of 使う.

• dictionary form: 使う = to use
• potential form: 使える = can use / be usable
• polite potential: 使えます

So まだ使えます literally means:

• can still use or
• is still usable

With an object like a computer, English often sounds more natural as:

• it still works
• it is still usable
• you can still use it

It can suggest any of those depending on context, but in this sentence the most natural meaning is:

• it is still usable
• you can still use it
• it still works

Because the topic is this computer, the sentence is describing the computer’s condition. So 使えます is not mainly about the speaker’s personal ability. It is about the computer being usable.

Japanese often leaves out things that are obvious from context.

In English, we might say:

• You can still use it.

In Japanese, once this computer has already been made the topic, there is no need to repeat it.

So:

• このパソコンは古いですが、まだ使えます。

naturally implies:

• As for this computer, it’s old, but it’s still usable.

A helpful breakdown is:

• このパソコンは = As for this computer,
• 古いです = it is old
• が = but
• まだ = still
• 使えます = can be used / can still be used

So the full flow is:

As for this computer, it is old, but it is still usable.

This is very typical Japanese sentence structure:

• topic first
• description
• connector
• final verb/adjective at the end

Yes. A casual version would be:

• このパソコンは古いけど、まだ使える。

Changes:

• です is removed
• が becomes the more casual けど
• 使えます becomes plain form 使える

The meaning stays the same:

• This computer is old, but it’s still usable.

The comma marks a pause after ですが and makes the sentence easier to read.

• このパソコンは古いですが、まだ使えます。

Japanese punctuation is sometimes more flexible than English punctuation, but this comma is very natural because the sentence has two contrasting parts:

1. it is old
2. it is still usable

So the comma helps separate those ideas clearly.