sensei ha tiisana matigai nara sugu ni yurusite kureru ga, onazi matigai wo nando mo suru to sikaru.

小さな is a special form used directly before a noun, much like a な-adjective form, even though 小さい is normally an い-adjective.

So both of these can exist:

• 小さい間違い
• 小さな間違い

In practice, 小さな often sounds a little more literary, descriptive, or set-phrase-like. Here it means something like a minor/small mistake.

This same pattern also happens with 大きな / 大きい.

Here, なら follows the noun 間違い and means something like:

• if it is a mistake
• when it comes to mistakes
• if it's just a mistake

So 小さな間違いなら means:

• if it's a small mistake
• as long as it's only a minor mistake

In this sentence, なら sets up the condition under which the teacher forgives.

なら is often used when the speaker takes something as a given and comments on it.

Here, the idea is:

• if it's a small mistake, then...

It has a natural “in that case” feeling.

Compared with other conditionals:

• たら: often feels more like when/after it happens
• ば: often sounds more general or logical
• なら: often sounds like if that’s the case / given that

So 小さな間違いなら is a very natural way to say if it’s a minor mistake.

Yes, it can be just すぐ.

Both are natural:

• すぐ許してくれる
• すぐに許してくれる

The に is optional here and makes it sound slightly more adverbial or a bit more polished. The meaning does not really change: immediately / right away.

許す simply means to forgive.

許してくれる adds the helper/giving nuance of くれる, which often means someone does something for the speaker or the speaker’s side.

So:

• 許す = forgives
• 許してくれる = forgives us / forgives someone on our side, with a nuance that it is a favorable action

In this sentence, it suggests that the teacher kindly forgives small mistakes.

This 〜てくれる pattern is very common when someone does something beneficial for the speaker or their in-group.

Here が works like but:

• The teacher forgives small mistakes quickly, but...

It connects two clauses with contrast:

1. the teacher forgives small mistakes
2. the teacher scolds if the same mistake is repeated

This が is a bit more formal or written-sounding than casual けど.

同じ is a special word. When it comes before a noun, it usually appears directly without な:

• 同じ間違い = the same mistake

Even though 同じ can behave somewhat like a na-adjective, before nouns it is very commonly used as just 同じ + noun.

So 同じ間違い is the normal form.

何度も means:

• many times
• again and again
• repeatedly

It is made from:

• 何度 = how many times
• も = adds an emphatic sense, giving the idea of so many times / over and over

So 同じ間違いを何度もする means to make the same mistake many times.

Yes, in many cases 何度も and 何回も are very similar and both can mean many times / repeatedly.

In this sentence, either would sound natural:

• 同じ間違いを何度もする
• 同じ間違いを何回もする

何度も may sound a little more natural in some written contexts, but the difference is small here.

This と is a conditional, meaning something like:

• if
• when

So:

• 同じ間違いを何度もすると、叱る
• If you make the same mistake many times, [the teacher] scolds [you].

This と is often used for things that happen as a natural result, habitual result, or automatic consequence.

Here it gives the sense that repeated mistakes lead to scolding as a regular outcome.

It is not the と meaning and or with.

The object is omitted because it is obvious from context.

The teacher is scolding the person who makes the repeated mistake. In English we would say scolds them / scolds you / scolds the student, but Japanese often leaves that unstated when it is clear.

So the full idea is something like:

• If someone makes the same mistake again and again, the teacher scolds them.

Because 先生は is the topic at the start of the sentence, and that topic continues unless something changes.

So after 先生は, the listener naturally understands that the later verb 叱る also refers to the teacher.

Japanese often omits repeated subjects and topics when they are already understood.

It most naturally sounds like a general rule or habitual behavior:

• The teacher forgives small mistakes quickly,
• but scolds when the same mistake is made repeatedly.

The plain present forms and the conditional structure give it a general, timeless feel rather than describing one single incident.

Not really. Here small means minor, trivial, or not serious.

So 小さな間違い is best understood as:

• a minor mistake
• a small error
• a little mistake

This is similar to English, where small mistake usually means not a serious one, not something physically small.