Если банан уже мягкий, он обычно слаще, чем груша.

In Russian, the present-tense form of to be is usually omitted.

So:

• банан мягкий = the banana is soft / a banana is soft
• он обычно слаще = it is usually sweeter

This is completely normal. Russian only uses forms of быть more visibly in the past, future, or in certain special constructions.

Russian does not have articles.

So банан can mean:

• a banana
• the banana
• sometimes just banana in a general sense

You understand which one is meant from context. In this sentence, English might say a banana or the banana, but Russian simply says банан.

Because it has to agree with банан.

Банан is:

• masculine
• singular
• nominative

So the adjective also has to be masculine singular nominative:

• мягкий = soft for a masculine noun

Compare:

• мягкий банан = soft banana
• мягкая груша = soft pear
• мягкое яблоко = soft apple
• мягкие бананы = soft bananas

Если usually means if.

So:

• Если банан уже мягкий... = If the banana is already soft...

In sentences like this one, especially with обычно, it can sound like a general truth or tendency:

• If a banana is already soft, it is usually sweeter...

So it is still if, but the whole sentence can describe something that is generally true.

Уже usually means already.

Here it suggests that the banana has reached that state by now:

• уже мягкий = already soft

It often gives a sense of by this point or now that it has become soft.

A few examples:

• Он уже дома. = He is already home.
• Банан уже мягкий. = The banana is already soft.

Он means he/it, and here it means it, referring back to банан.

Since банан is masculine, the pronoun is masculine too:

• банан → он

Russian sometimes drops subject pronouns when the meaning is obvious, but here он sounds natural because it clearly restates the subject of the second clause.

So:

• Если банан уже мягкий, он обычно слаще... = natural
• leaving out он here would sound less complete

Обычно means usually. It modifies the whole idea: the banana is usually sweeter in that situation.

Its position is fairly flexible, but this placement is very natural:

• он обычно слаще, чем груша

Other placements are possible, depending on emphasis, for example:

• он слаще обычно, чем груша would sound odd in this sentence
• обычно он слаще, чем груша is also possible

So the version in the sentence is a normal, neutral word order.

Because слаще is the comparative form: sweeter.

• сладкий = sweet
• слаще = sweeter

Russian often forms comparatives with a special one-word form instead of using something like more + adjective.

So:

• банан сладкий = the banana is sweet
• банан слаще = the banana is sweeter

This is one of the very common Russian comparative patterns.

Some Russian comparatives are irregular or partly irregular.

For сладкий, the comparative is:

• слаще

This is just a form you need to learn as part of the adjective. Many common adjectives do something similar:

• большой → больше = bigger, more
• маленький / малый → меньше = smaller, less
• хороший → лучше = better
• сладкий → слаще = sweeter

So yes, the change is bigger than in English, but it is a normal comparative form.

Yes, but слаще is more natural here.

Both can mean sweeter:

• он слаще, чем груша
• он более сладкий, чем груша

But the short comparative слаще is usually the more everyday and idiomatic choice in a simple sentence like this.

Чем means than in comparisons.

So:

• слаще, чем груша = sweeter than a pear

After чем, Russian often uses the noun in the nominative form, which is why you see груша.

There is also another common pattern without чем:

• он слаще груши

In that version, груши is genitive.

So both are possible:

• слаще, чем груша
• слаще груши

The sentence you were given uses the чем + nominative pattern.

Because Если банан уже мягкий is a subordinate clause introduced by если.

Russian normally puts a comma between the if-clause and the main clause:

• Если банан уже мягкий, он обычно слаще, чем груша.

This is standard punctuation.

If the order were reversed, the comma would still be there:

• Он обычно слаще, чем груша, если банан уже мягкий.

Yes, Russian word order is fairly flexible, but different orders can sound more or less natural.

The given sentence is neutral and natural:

• Если банан уже мягкий, он обычно слаще, чем груша.

You could also say:

• Банан, если он уже мягкий, обычно слаще, чем груша.

That has a slightly different rhythm and emphasis, but the meaning is close.

So yes, word order can move around, but the original version is a very normal way to say it.