Mi profesora me dijo que, en caso de que escribiera demasiado deprisa, leyera el texto otra vez para comprobar las comillas, los paréntesis y las tildes.

Because me means to me. Spanish often uses an indirect object pronoun with decir.

So:

• Mi profesora dijo... = My teacher said...
• Mi profesora me dijo... = My teacher told me / said to me...

In this sentence, the teacher is addressing the speaker directly, so me is necessary.

Because after decirle a alguien to report an order, instruction, or advice, Spanish normally uses:

decirle a alguien que + subjunctive

So:

• Direct speech: Lee el texto otra vez
• Reported speech: Mi profesora me dijo que leyera el texto otra vez

This is one of the standard ways Spanish reports commands. English often uses told me to read, but Spanish usually uses me dijo que leyera.

Because this is reported advice or a reported command, not a simple statement of fact.

After me dijo que, if what follows is an instruction, request, order, or recommendation, Spanish uses the subjunctive:

• Me dijo que estudiara
• Me dijo que esperara
• Me dijo que leyera

Here, leyera means something like that I should read or to read in reported speech.

Because en caso de que is a fixed expression that requires the subjunctive.

It means in case or in the event that, and it introduces a situation that is possible, hypothetical, or not yet confirmed. Spanish treats that kind of idea as non-factual, so it uses the subjunctive.

Examples:

• En caso de que llueva...
• En caso de que tengas dudas...
• En caso de que escribiera demasiado deprisa...

So escribiera is there because en caso de que calls for the subjunctive.

Because the main verb is in the past: me dijo.

Spanish often shifts the subjunctive back when the reporting verb is in the past. This is a very common sequence-of-tenses pattern.

Compare:

• Present reporting: Mi profesora me dice que, en caso de que escriba demasiado deprisa, lea el texto otra vez
• Past reporting: Mi profesora me dijo que, en caso de que escribiera demasiado deprisa, leyera el texto otra vez

So the imperfect subjunctive here does not mean the action happened in the past in the usual sense. It is mostly there because the whole instruction is being reported from a past point of view.

They are both forms of the imperfect subjunctive.

A common way to form this tense is:

1. Take the ellos/ellas/ustedes form of the preterite
2. Remove -ron
3. Add the imperfect subjunctive endings

For these verbs:

• escribir → preterite escribieron → remove -ron → escribie- → escribiera
• leer → preterite leyeron → remove -ron → leye- → leyera

Spanish also has an alternative -se form:

• escribiese
• leyese

These are equivalent in meaning, though -ra forms are more common in everyday use.

Sometimes yes, but the nuance is a little different.

• si = if
• en caso de que = in case / in the event that

En caso de que sounds more formal and more precautionary. It suggests preparing for a possible situation.

Also, grammatically:

• en caso de que takes the subjunctive
• si does not normally take the subjunctive in this type of sentence

So you could say something like:

• Si escribía demasiado deprisa, leyera... is not the natural equivalent here
• A more direct version would be something like Si escribes demasiado deprisa, lee el texto otra vez

But the sentence you were given is more formal and uses the specific structure en caso de que + subjunctive.

Because the subject is the same.

The idea is:

• the same person would read
• and that same person would check

When the subject stays the same, Spanish normally uses:

para + infinitive

So:

• leyera el texto otra vez para comprobar...

If the subject changed, then Spanish would use:

para que + subjunctive

For example:

• Le di el texto para que lo comprobara la profesora

There, the person giving the text and the person checking it are different, so para que is needed.

More or less, yes, but the usage is slightly different.

• deprisa = quickly / in a hurry
• rápidamente = quickly, more neutral or a bit more formal
• rápido is often used adverbially in everyday speech, though strictly speaking it is an adjective

With escribir, deprisa is very natural, especially in Spain:

• escribir deprisa
• hablar deprisa

It often gives the sense of doing something too fast, perhaps carelessly or hurriedly.

So demasiado deprisa is very natural here: too quickly / too fast.

Because these are three separate noun groups, and they do not all have the same gender.

• las comillas — feminine plural
• los paréntesis — masculine plural
• las tildes — feminine plural

Since the genders change, repeating the article is the normal and clearest option.

In English, we can often say quotation marks, parentheses and accent marks with no article. Spanish more often uses definite articles when talking about categories of things like punctuation marks.

They are names of writing or punctuation features:

• comillas = quotation marks
• paréntesis = parentheses / brackets in the everyday sense of round brackets
• tildes = written accent marks, like the mark on á, é, í, ó, ú

A useful note: tilde is specifically the written accent mark, not a person’s accent in speech. So here the teacher is telling the student to check spelling and punctuation details.

Because that whole part is inserted into the middle of the sentence as a kind of parenthetical conditional phrase.

The main structure is:

Mi profesora me dijo que leyera el texto otra vez para comprobar...

Into that, the sentence inserts:

en caso de que escribiera demasiado deprisa

The commas help the reader see that this is an interruption or inserted condition. They make the sentence easier to process, especially because it is fairly long.

A direct version would be something like:

En caso de que escribas demasiado deprisa, lee el texto otra vez para comprobar las comillas, los paréntesis y las tildes.

Notice the changes:

• escribiera → escribas
• leyera → lee

That is because direct speech uses the forms appropriate to the original instruction, while reported speech shifts them into the imperfect subjunctive after me dijo que.