atarasii sensei no setumei ha zuibun wakariyasukute, mae yori zyugyou ga tanosiku natta.

の links 先生 and 説明. Here it means something like the new teacher’s explanation(s) or the explanations by the new teacher.

A very literal breakdown is:

• 新しい = new
• 先生 = teacher
• の = linking particle
• 説明 = explanation / explanations

In English, this may come out as either singular or plural depending on context.

は marks 説明 as the topic of the first part of the sentence.

So 新しい先生の説明は means something like:

• As for the new teacher’s explanations...

This sets up what the speaker is going to say about those explanations, namely that they are ずいぶん分かりやすくて.

ずいぶん means quite, considerably, or a lot more than expected.

In this sentence, it adds emphasis:

• ずいぶん分かりやすい = quite easy to understand / much easier to understand

It often carries the nuance that the difference is noticeable.

分かりやすい comes from:

• 分かる = to understand
• 〜やすい = easy to do

So:

• 分かりやすい = easy to understand

This is a very common pattern in Japanese:

• 読みやすい = easy to read
• 話しやすい = easy to talk with / easy to speak
• 使いやすい = easy to use

Even though English speakers may expect something like understandable, Japanese often expresses this as easy to understand.

Because 分かりやすくて is the て-form of the い-adjective 分かりやすい.

For い-adjectives:

• 楽しい → 楽しくて
• おもしろい → おもしろくて
• 分かりやすい → 分かりやすくて

Here, 〜くて connects this part to the next part of the sentence.

So the sentence is linking:

• the new teacher’s explanations are quite easy to understand
• and, as a result, classes became more enjoyable

It can suggest both connection and reason.

In this sentence, 分かりやすくて sounds like more than just a simple and. It strongly suggests a causal link:

• The new teacher’s explanations are easy to understand,
• so / and because of that, classes became more enjoyable.

Japanese often leaves that cause-and-effect relationship slightly implicit, but it is still felt very naturally here.

より is the standard particle for comparison, meaning than.

So:

• 前より = than before

This compares the current situation with an earlier one.

A fuller English sense is:

• more than before
• than it was previously

Japanese often uses 前より in a natural, conversational way instead of something more formal like 以前より.

Because 前 here means before in a general time sense, not the previous noun.

• 前より = than before
• 前の授業 = the previous class

So if 前 directly modifies a noun, you usually use 前の.
But in 前より, it is part of a comparison expression, so の is not needed.

Here 授業が楽しくなった treats 授業 as the thing that underwent the change.

• 授業が楽しくなった = classes became enjoyable

Using が is natural because it marks what became that way.

If you used 授業は, it could sound more contrastive, like:

• As for classes, they became enjoyable
  perhaps implying contrast with something else.

So が is a straightforward, neutral choice here.

Because when an い-adjective is used before なる, it changes to its 〜く form.

Pattern:

• 楽しい → 楽しくなる = become enjoyable
• 高い → 高くなる = become expensive / become high
• 寒い → 寒くなる = become cold

So:

• 楽しいなった is incorrect
• 楽しくなった is correct

This is a very important pattern in Japanese grammar.

なった is the past form of なる, meaning became.

So 授業が楽しくなった means:

• classes became enjoyable
• class has become more enjoyable

It shows a change from an earlier state to a new one.
The sentence is not just saying the class is fun; it is saying it became fun.

Japanese often leaves the subject unstated when it is clear from context.

This sentence does not explicitly say I think or for the students. But the natural interpretation is that the speaker, or the people in the class, feel that the classes are more enjoyable now.

That omission is very normal in Japanese. English usually wants an explicit subject more often than Japanese does.

Japanese nouns usually do not mark singular vs. plural the way English does.

So 授業 could mean:

• class
• classes
• lessons

In this sentence, English might naturally translate it as classes or the lessons, because it sounds like an ongoing change in the course, not just one single class. But Japanese itself does not force that distinction.