Если кожа чувствительная, лучше выбирать мягкое мыло.

Если means if. It introduces a condition:

• Если кожа чувствительная, ... = If the skin is sensitive, ...

Russian uses если for conditional statements, just like English if.

Когда means when, so it would sound different:

• Когда кожа чувствительная, ... = When the skin is sensitive, ...

That is possible in some contexts, but если is the most natural choice for general advice like this.

Russian adjectives can have a full form and, for many adjectives, a short form.

Here:

• чувствительная = full form
• чувствительна = short form

Both can sometimes mean sensitive, but they are used a little differently.

In this sentence, кожа чувствительная sounds like describing a general characteristic: the skin is sensitive / the skin is of a sensitive type.

The short form кожа чувствительна is also grammatical, but it often sounds more like stating a condition or property in a more formal or concise way.

So:

• кожа чувствительная = very natural in everyday language
• кожа чувствительна = also possible, slightly different in tone

Russian often leaves out words like your, my, or the when the meaning is clear from context.

So:

• Если кожа чувствительная... literally looks like If skin is sensitive...
• but naturally it means If your skin is sensitive... or If the skin is sensitive..., depending on context

This is very common in Russian. Possessive words are only added when they are needed for clarity or emphasis.

For example:

• Если ваша кожа чувствительная... = If your skin is sensitive...

This version is more explicit, but the shorter sentence is perfectly normal.

This is a very common Russian structure for giving advice:

• лучше + infinitive

So:

• лучше выбирать = it is better to choose
• лучше сделать = it is better to do
• лучше подождать = it is better to wait

Russian often uses this without a subject. In English we usually say:

• it is better to choose
• you should choose

But in Russian, the sentence can stay impersonal:

• лучше выбирать мягкое мыло = it’s better to choose mild soap

The sentence is impersonal. Russian often gives advice without naming the person.

So лучше выбирать мягкое мыло does not literally say you, but the meaning is understood as something like:

• you should choose mild soap
• it is better to choose mild soap

If needed, Russian can make it more explicit:

• вам лучше выбирать мягкое мыло = it’s better for you to choose mild soap

But leaving out вам is very normal.

This is about aspect.

• выбирать = imperfective
• выбрать = perfective

In this sentence, выбирать is used because the advice is general or habitual:

• Если кожа чувствительная, лучше выбирать мягкое мыло.
• If your skin is sensitive, it’s better to choose mild soap.

This means: as a rule, when choosing soap, choose mild soap.

If you said лучше выбрать, it would sound more like a single completed choice:

• Лучше выбрать мягкое мыло. = It’s better to choose mild soap (for this one decision)

So:

• выбирать = general recommendation / repeated situation
• выбрать = one-time choice

Because мягкое agrees with мыло.

Russian adjectives change their endings to match the noun in:

• gender
• number
• case

Here, мыло is:

• neuter
• singular
• accusative (but for an inanimate neuter noun, accusative looks the same as nominative)

So the adjective also has the neuter singular ending:

• мягкое мыло = mild soap

Compare:

• мягкий шампунь = masculine
• мягкая пенка = feminine
• мягкое мыло = neuter

Yes, it is the accusative.

The verb выбирать takes a direct object, so мыло is in the accusative case.

However, for inanimate neuter singular nouns, the accusative form is the same as the nominative form.

So:

• nominative: мыло
• accusative: мыло

That is why the form does not change.

Because кожа is the subject of the clause:

• Если кожа чувствительная...

Here, кожа is what is being described as sensitive, so it stands in the nominative case.

You can think of it as:

• skin is sensitive
• subject = skin = nominative

So:

• кожа = nominative singular
• чувствительная agrees with it in feminine singular nominative

Because Если кожа чувствительная is a subordinate clause introduced by если.

Russian punctuation requires a comma between the if-clause and the main clause:

• Если кожа чувствительная, лучше выбирать мягкое мыло.

This is similar to English when the if-clause comes first:

• If your skin is sensitive, it’s better to choose mild soap.

So the comma is required.

Yes, Russian word order is flexible.

The neutral order here is:

• Если кожа чувствительная, лучше выбирать мягкое мыло.

But other orders are possible, for example:

• Если кожа чувствительная, мягкое мыло лучше выбирать.

This still means basically the same thing, but it may place a little more emphasis on мягкое мыло.

Russian changes word order more freely than English, but the original version is the most natural and standard for a learner to use.

Not always. In this sentence, мягкое мыло means mild soap, not physically soft soap.

Russian мягкий / мягкое can mean:

• soft in the physical sense
• gentle
• mild

With skincare products, it often means gentle or non-harsh.

So here мягкое мыло is best understood as:

• mild soap
• gentle soap

A natural stress pattern would usually highlight the important information:

• Если кóжа чувствительная, лýчше выбирать мЯгкое мЫло.

Useful word stress:

• е́сли
• кóжа
• чувстви́тельная
• лýчше
• выбира́ть
• мя́гкое
• мы́ло

Stress is important in Russian, because it is not always predictable from spelling.