kono kikai wo tukau mae ni, setumeisyo wo yonda hou ga ii desu.

When a verb comes before 前に to mean before doing ..., Japanese uses the dictionary form of the verb.

• 使う前に = before using
• 食べる前に = before eating
• 寝る前に = before sleeping

So:

• この機械を使う前に = before using this machine

This is different from English, where we often use before using with an -ing form.

前 means before or in front, and に marks the time point.

In this sentence, 前に means before in a time sense:

• 使う前に = before using

A useful pattern is:

• verb dictionary form + 前に = before doing something
• noun + の + 前に = before something

Examples:

• 寝る前に、歯を磨きます。 = I brush my teeth before sleeping.
• 食事の前に、手を洗います。 = I wash my hands before the meal.

〜たほうがいい is a very common pattern meaning it would be better to... or you should...

So:

• 読んだほうがいい = you should read (it) / it’s better to read (it)

Even though 読んだ is the past form by itself, in this grammar pattern it does not mean past time. It is just the form required for giving advice.

Compare:

• 薬を飲んだほうがいいです。 = You should take the medicine.
• 早く寝たほうがいいです。 = You should go to bed early.

読むほうがいい can exist in some contexts, but it usually sounds more like reading is better than some other option, not the standard advice pattern used here.

No, it is usually softer than must.

〜ほうがいいです means something like:

• you should...
• it would be better to...
• it’s advisable to...

So this sentence is giving advice or a recommendation, not a strict order.

If you wanted a much stronger meaning like must, Japanese would use different expressions, such as:

• 〜なければならない
• 〜なくてはいけない

So 説明書を読んだほうがいいです is closer to You should read the manual than You must read the manual.

Because there are two different verbs, and each verb has its own object.

1. この機械を使う

   • この機械 = this machine
   • を marks this machine as the object of 使う (to use)

2. 説明書を読んだほうがいいです

   • 説明書 = manual/instructions
   • を marks manual as the object of 読む (to read)

So the sentence contains two separate action phrases:

• this machine + use
• manual + read

That is why を appears twice.

This is very normal in Japanese.

The sentence is polite overall because it ends with です:

• 読んだほうがいいです

But verbs that come inside a modifier often stay in the plain form. Here, 使う modifies 前:

• 使う前に = before using

So Japanese often mixes:

• plain form inside grammar structures
• polite form at the end of the sentence

This is standard and natural.

In 〜ほうがいい, the が is part of the fixed expression.

Literally, ほう means something like side or option, and ほうがいい originally has the sense of the option of doing X is good. In modern Japanese, learners should usually just treat 〜たほうがいい as one grammar pattern meaning:

• should do
• had better do
• it’s better to do

So in this sentence:

• 読んだほうがいいです = You should read it

You do not need to translate が separately every time.

Yes. In fact, it is very natural to omit it.

Japanese often leaves out subjects when they are obvious from context. This sentence does not explicitly say you, but the meaning is understood as something like:

• Before using this machine, you should read the manual.

Depending on context, it could also mean:

• one should read the manual
• people should read the manual

Japanese often sounds less direct by leaving the subject unstated.

説明書 means instruction manual, guide, or written instructions.

It is made of:

• 説明 = explanation
• 書 = writing/document

So for a machine, 説明書 is the manual that explains how to use it.

It is more specific than just book.

Yes. A casual version would be:

• この機械を使う前に、説明書を読んだほうがいい。

The only change is dropping です at the end.

That makes it plain/casual, but the grammar is the same:

• 使う前に = before using
• 読んだほうがいい = should read

A very direct command would be different, for example:

• この機械を使う前に、説明書を読んでください。 = Please read the manual before using this machine.

That sounds more like an instruction than advice.