houkago ni midori no sibahu de rensyuusureba, yakyuu ga zyouzu ni naru.

Here, 放課後に means after school as a time expression.

The particle に marks a specific time when something happens. So:

• 放課後に = after school
• 練習する = to practice

Together, 放課後に練習する means to practice after school.

A learner may notice that some time words do not need に. That is true. For example, words like 今日 or 毎日 often appear without it. But with a noun like 放課後, using に is very common and natural.

緑の芝生 means green grass or a green lawn.

Breaking it down:

• 緑 = green
• 芝生 = lawn / grass / grassy area

The の links the two nouns, almost like saying grass of green color. In English we just say green grass, but in Japanese a noun like 緑 often uses の before another noun.

So:

• 緑の芝生 = green grass
• literally something like grass that is green

This is very normal Japanese.

The particle で marks the place where an action happens.

In this sentence, the action is 練習する (to practice), and the practicing happens on the grass. So:

• 芝生で練習する = practice on the grass

This is different from に, which often marks:

• destination
• exact time
• existence in some cases

So compare:

• 公園で練習する = practice in/at the park
• 公園に行く = go to the park

Here, because practicing is an action happening in that place, で is the correct particle.

練習すれば is the conditional form of 練習する.

• dictionary form: 練習する = to practice
• conditional -ba form: 練習すれば = if [someone] practices

So the first part of the sentence means:

• 放課後に緑の芝生で練習すれば = if you practice on the green grass after school

This -ば form is one common way to say if in Japanese.

For する verbs:

• すれば = if [someone] does

Since 練習する is a suru-verb, it becomes:

• 練習すれば

Its main meaning here is if.

However, Japanese conditionals can sometimes feel broader than English. Depending on context, -ば can suggest things like:

• if
• whenever
• sometimes something close to when, if the result is expected

In this sentence, the meaning is basically:

• If you practice after school on the grass, you will get good at baseball.

It sounds like a general truth or recommendation: doing this leads to that result.

This is a very common question.

In Japanese, 上手 is used with が, not を, when talking about what someone is good at.

So:

• 野球が上手だ = someone is good at baseball
• ピアノが上手だ = someone is good at piano

Even though English says good at baseball, Japanese uses が with 上手.

That means:

• 野球が上手になる = become good at baseball

Using を here would be unnatural.

Because なる often combines with a na-adjective or noun-like word using に.

• 上手 is a na-adjective
• with なる, it becomes 上手になる = to become skilled / to become good

This is the same pattern as:

• 静かになる = become quiet
• 元気になる = become healthy / energetic
• きれいになる = become beautiful / clean

So:

• 上手に by itself can also mean skillfully
• but in 上手になる, the important thing is the set pattern Xになる = become X

Here the phrase means to become good/skilled, not to do something skillfully.

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

The sentence does not explicitly say:

• you
• he
• she
• one
• someone

From context, it is often understood as something like:

• if you practice..., you’ll get good at baseball
• or if someone practices..., they’ll get good at baseball

Japanese often leaves out subjects when they are obvious or not important.

So yes, in many learning contexts, this will naturally be understood as you.

The comma separates the if-clause from the main result.

So the structure is:

• 放課後に緑の芝生で練習すれば、 = if you practice after school on the green grass,
• 野球が上手になる。 = you will become good at baseball.

Japanese commas are often used a bit more flexibly than English commas, but here it helps make the sentence easier to read.

The structure is:

[time] + [place] + [conditional action] + [result]

More specifically:

• 放課後に = after school
• 緑の芝生で = on the green grass
• 練習すれば = if [someone] practices
• 野球が上手になる = [they] become good at baseball

So the whole sentence is built like:

If X happens, Y happens.

That is a very common Japanese pattern.

It means become good at baseball.

That is slightly different from directly saying play baseball well.

• 野球が上手になる focuses on improving your skill
• 野球を上手にする / 野球をうまくやる would be closer to do/play baseball skillfully, though those are different expressions

So this sentence is about gaining ability, not just describing one specific performance.

Yes. 芝生 usually refers to a grassy area, lawn, or turf, not just the abstract idea of grass.

So 緑の芝生で suggests practicing:

• on a green lawn
• on grassy ground
• on a field covered with grass

It gives a picture of the location rather than just naming the color green and the concept of grass separately.

Yes, it is understandable and grammatically fine.

It sounds like a general statement such as:

• If you practice after school on the grass, you’ll get good at baseball.

A native speaker might choose slightly different wording depending on what they want to emphasize, but nothing here is grammatically strange.

For example, a speaker might also say things like:

• 放課後に芝生で練習すれば、野球がうまくなる。
• 放課後に練習すれば、野球が上手になる。

But the original sentence is still a good example for studying particles and structure.