pasuwaado no tukaimawsi wo sake, pasuwaadokanriapuri wo tukau.

Not in normal Japanese writing. This sentence would usually be written as:

パスワードの使い回しを避け、パスワード管理アプリを使う。

Learning materials often add spaces to help beginners see the parts more clearly, but standard Japanese does not usually separate words with spaces the way English does.

It is read つかいまわし.

Grammatically, 使い回し is a noun. It comes from the verb 使い回す, which means something like to reuse repeatedly or to use the same thing again and again in different places.

So here, 使い回し means reuse or recycling the same password across multiple accounts.

The の links two nouns together.

• パスワード = password
• 使い回し = reuse

So パスワードの使い回し means password reuse or more literally the reuse of passwords.

This is a very common pattern in Japanese:

• 日本語の勉強 = study of Japanese
• 車の運転 = driving a car
• パスワードの使い回し = reuse of passwords

Because the sentence is built around 避ける, which means to avoid. Japanese often uses a noun before 避ける:

• 使い回しを避ける = avoid reuse

If you used the verb instead, you would need a different structure, such as:

• パスワードを使い回すのを避ける
• パスワードを使い回さない

So the version in your sentence is compact and natural, especially in warnings, guidelines, and security advice.

Because 使い回し is the direct object of 避ける.

• 使い回しを避ける = avoid reuse

The particle を marks what is being avoided.

Then later:

• パスワード管理アプリを使う = use a password management app

So this sentence has two separate を phrases, one for each verb:

• 使い回しを → object of 避ける
• パスワード管理アプリを → object of 使う

避け、 is a more written, formal-looking way to connect to the next action. It is the continuative form of 避ける and functions a lot like 避けて here.

So these are very close in meaning:

• パスワードの使い回しを避け、パスワード管理アプリを使う。
• パスワードの使い回しを避けて、パスワード管理アプリを使う。

The version with 避け、 sounds more like something you would see in:

• instructions
• manuals
• posters
• security guidelines
• article headings

The comma helps show the pause between the two linked actions.

Not exactly a direct command in the same way as 使え would be. It is the plain dictionary form, but in this kind of context it works like instructional style or general advice.

So it feels like:

• concise guidance
• policy language
• written recommendation

That is why it can sound like Avoid reusing passwords; use a password manager app even though it is not a harsh command form.

If you wanted a more openly polite version, you might say:

• パスワードの使い回しを避けて、パスワード管理アプリを使いましょう。
• パスワードの使い回しを避け、パスワード管理アプリを使ってください。

Japanese often leaves out the subject when it is obvious from context.

In a sentence like this, the implied subject is something like:

• you
• people in general
• users

Because this is advice or instruction, Japanese does not need to say あなたは. In fact, saying あなたは here would often sound less natural unless you specifically wanted emphasis.

Yes. It is a compound noun:

• パスワード = password
• 管理 = management
• アプリ = app

So パスワード管理アプリ means password management app, or naturally in English, password manager app / password manager.

Japanese very often combines nouns this way without extra words in between.

Because they are loanwords.

• パスワード comes from password
• アプリ comes from application/app

Katakana is commonly used for foreign-origin words in Japanese. Meanwhile:

• 使う
• 避ける
• 管理

are regular Japanese words written with kanji and hiragana.

Yes. A few common alternatives are:

• パスワードを使い回さず、パスワード管理アプリを使う。
  This uses the negative continuative form 使い回さず = without reusing.

• パスワードを使い回すのを避け、パスワード管理アプリを使う。
  This keeps 使い回す as a verb and turns it into a noun-like phrase with の.

• 同じパスワードを使い回さず、パスワード管理アプリを使う。
  This makes the idea of the same password explicit.

Your original sentence is especially compact and natural for security-related writing.