Если стелька мокрая, я сушу обувь у батареи до утра.

In Russian, the verb to be is usually omitted in the present tense.

So:

• стелька мокрая = the insole is wet
• literally, Russian just says insole wet

If you wanted past or future, a form of быть would appear:

• Стелька была мокрая = The insole was wet
• Стелька будет мокрая = The insole will be wet

Because мокрая has to agree with стелька.

Стелька is:

• feminine
• singular
• nominative

So the adjective must also be:

• feminine
• singular
• nominative

That gives мокрая.

Compare:

• мокрый = masculine
• мокрая = feminine
• мокрое = neuter
• мокрые = plural

It is in the nominative case because it is the subject of the clause:

• стелька мокрая = the insole is wet

The noun being described as wet is the subject, so nominative is the normal case here.

Because сушить takes a direct object, so обувь is in the accusative case.

However, обувь is an inanimate feminine noun, and for many feminine nouns ending in a soft sign, the nominative and accusative singular look the same.

So:

• nominative: обувь
• accusative: обувь

Even though the form looks unchanged, its role in the sentence is object:

• я сушу обувь = I dry the shoes/footwear

Сушу is from the imperfective verb сушить. It is often used for:

• repeated actions
• habitual actions
• general statements
• process-focused actions

So this sentence sounds like a normal, general habit:

• If the insole is wet, I dry the shoes by the radiator until morning.

If you said высушу, that would be perfective and would emphasize completing the drying:

• я высушу обувь = I will dry the shoes completely

That would usually fit a more specific one-time situation, not a general routine.

Usually yes, but depending on context it can sometimes feel close to when in English, especially in general-condition statements.

Here it is best understood as if:

• Если стелька мокрая, я сушу обувь...
• If the insole is wet, I dry the shoes...

It describes a condition that leads to an action.

Because Russian normally separates an если clause from the main clause with a comma.

So the structure is:

• Если стелька мокрая, = subordinate clause
• я сушу обувь у батареи до утра. = main clause

This is standard Russian punctuation.

Here у means by, near, or next to.

So:

• у батареи = by the radiator

After у, Russian uses the genitive case, so:

• dictionary form: батарея
• after у: у батареи

Yes, but the meaning changes slightly.

• у батареи = by / near the radiator
• на батарее = on the radiator

So the sentence with у батареи suggests the shoes are placed close to the radiator.
If you say на батарее, it sounds like they are physically on top of it.

Both are possible in real life, but they are not exactly the same.

No, here it means radiator.

In Russian, батарея can mean:

• a battery
• a radiator
• sometimes a set of artillery guns in military contexts

In everyday home-related language, у батареи almost always means by the radiator.

It is genitive, because the preposition до requires the genitive case.

So:

• dictionary form: утро
• after до: до утра

До утра means until morning.

Other examples:

• до вечера = until evening
• до дома = as far as the house / up to the house

Yes, but Russian can still use the singular if the speaker is thinking about one insole being wet.

This sentence means something like:

• if an insole is wet, I dry the shoes

If you wanted to talk about both insoles, you could say:

• Если стельки мокрые, я сушу обувь у батареи до утра.

That would mean:

• If the insoles are wet, I dry the shoes by the radiator until morning.

Yes. Russian word order is flexible, though not random.

The neutral order here is very natural:

• Если стелька мокрая, я сушу обувь у батареи до утра.

But other orders are possible for emphasis, for example:

• Я сушу обувь у батареи до утра, если стелька мокрая.

That puts the main action first and the condition afterward.

So the meaning stays basically the same, but the emphasis and flow can change.

Yes, мокра is possible, but it sounds less neutral in everyday speech.

Compare:

• стелька мокрая = the most natural everyday version
• стелька мокра = grammatically correct, but more literary or stylistically marked

In modern spoken Russian, full adjective forms like мокрая are very common in this kind of predicate sentence.

The main stress pattern is:

• Е́сли сте́лька мокра́я, я сушу́ о́бувь у батаре́и до утра́.

A few useful notes:

• если → stress on the first syllable
• стелька → stress on сте́ль-
• мокрая → stress on -кра́-
• сушу → stress on the last syllable
• обувь → stress on the first syllable
• батареи → stress on -ре́-
• утра → stress on the last syllable

This is worth learning early, because stress in Russian is unpredictable and can change from form to form.