kono bun ha wakariyasui desu.

It is read:

この ぶん は わかりやすい です。

In normal writing, it would usually appear without spaces:

この文は分かりやすいです。

A very natural pronunciation is kono bun wa wakariyasui desu.

No. Standard Japanese normally does not use spaces between words.

So in real Japanese writing, you would usually see:

この文は分かりやすいです。

Spaces are often added in beginner materials to make the structure easier to see.

この means this when it comes directly before a noun.

So:

この文 = this sentence

By contrast, これ stands alone and does not directly modify a noun.

• この文 = this sentence
• これ = this / this one

So この文 is correct here because 文 is the noun being modified.

When は is used as the topic particle, it is pronounced wa, not ha.

So in this sentence:

この文は is read このぶんは / kono bun wa

This is just a standard feature of Japanese spelling. The character is still written は, but the pronunciation is wa when it marks the topic.

Here, 文 is read ぶん.

In this sentence, it means sentence.

So:

この文 = this sentence

Depending on context, 文 can sometimes refer more broadly to a piece of writing or a passage, but sentence is the most natural meaning here.

分かりやすい is an -i adjective.

It comes from:

• 分かる = to understand / to be understandable
• -やすい = easy to do

So 分かりやすい literally means something like easy to understand.

This pattern is very common in Japanese:

• 読みやすい = easy to read
• 食べやすい = easy to eat
• 使いやすい = easy to use

Yes, 分かりやすい is already complete.

An -i adjective can end a sentence by itself:

この文は分かりやすい。

Adding です makes it polite:

この文は分かりやすいです。

So here, です is mainly adding politeness. It is not exactly the same as English is.

This is an important point: Japanese adjectives can act as the predicate of the sentence without needing a separate word meaning is.

は marks この文 as the topic:

As for this sentence, it is easy to understand.

That is a very natural choice here.

If you used が instead, it would sound more focused or contrastive, as if you were identifying this sentence specifically as the one that is easy to understand.

So:

• この文は分かりやすいです。 = This sentence is easy to understand. / As for this sentence, it’s easy to understand.
• この文が分かりやすいです。 = This sentence is the easy-to-understand one. / It is this sentence that is easy to understand.

For a simple neutral statement, は is the more expected choice.

Japanese often mixes kanji and kana in the same word.

In 分かりやすい:

• 分 is the kanji part
• かりやすい is written in kana

This is very normal. The kana after the kanji are called okurigana.

Yes, it can also be written fully or mostly in hiragana:

わかりやすい

In fact, many people often write this word in hiragana, especially in everyday writing. So both of these are natural:

• この文は分かりやすいです。
• この文はわかりやすいです。

The casual version is:

この文は分かりやすい。

You simply remove です.

So:

• この文は分かりやすいです。 = polite
• この文は分かりやすい。 = casual

Because 分かりやすい is an -i adjective, it changes like this:

• Negative: この文は分かりやすくないです。 = This sentence is not easy to understand.
• Past: この文は分かりやすかったです。 = This sentence was easy to understand.
• Past negative: この文は分かりやすくなかったです。 = This sentence was not easy to understand.

This is a useful pattern to learn for all -i adjectives.