Antes de enviar el informe, reviso el borrador con mi tutora.

Because after antes de, Spanish normally uses an infinitive when the subject stays general or is understood:

• Antes de enviar el informe... = Before sending the report... / Before I send the report...

So:

• antes de + infinitive is the normal pattern
• enviar is the infinitive, so it fits perfectly

Antes de envío is wrong because envío is a noun or a verb form, not an infinitive.

Antes que enviar is also wrong here. Spanish uses antes de before an infinitive, not antes que.

You can say:

• Antes de enviar el informe...
  or
• Antes de que envíe el informe...

The second version is more explicit because it uses a full clause:

• antes de + infinitive
• antes de que + subjunctive

So:

• Antes de enviar el informe, reviso el borrador...
• Antes de que envíe el informe, reviso el borrador...

Both can mean Before I send the report, I review the draft...

A learner should know that antes de que requires the subjunctive, so envíe is used, not envío.

Reviso is the first-person singular present of revisar:

• yo reviso = I review / I check

Spanish often uses the present tense for:

• habits
• routines
• things that generally happen

So this sentence likely means something like:

• Before sending the report, I review the draft with my supervisor
  as a regular procedure or usual action.

It does not have to mean only what is happening right now.

Because Spanish usually drops subject pronouns when the verb already makes the subject clear.

• reviso already tells you the subject is yo
• so Yo reviso is possible, but not necessary

Spanish is a pro-drop language, which means subject pronouns are often omitted unless needed for:

• emphasis
• contrast
• clarity

So:

• Reviso el borrador... = natural
• Yo reviso el borrador... = more emphatic, like I’m the one who reviews it

Spanish often uses the definite article when talking about something specific or already understood in context.

So here:

• el informe = the report
• el borrador = the draft

This suggests the speaker and listener both know which report and which draft are being discussed.

If you said:

• un informe
• un borrador

that would sound more like a report or a draft, not a specific one.

Here borrador means draft.

In work or academic contexts, el borrador is a preliminary version of a text before the final version is sent.

Examples:

• Es solo un borrador. = It’s only a draft.
• Revisa el borrador antes de enviarlo. = Check the draft before sending it.

Be careful: borrador can also mean eraser in some contexts, but in this sentence draft is clearly the correct meaning.

Tutora is the feminine form of tutor.

It can mean things like:

• tutor
• mentor
• academic supervisor
• adviser

The exact English translation depends on context.

So:

• mi tutor = my male tutor/supervisor
• mi tutora = my female tutor/supervisor

And con mi tutora means:

• with my tutor/supervisor
• or together with my tutor/supervisor

The preposition con simply means with.

Yes, it is normal in Spain, especially in educational contexts.

In Spain, tutor or tutora can refer to:

• a school tutor responsible for a class
• an academic adviser
• a dissertation or internship supervisor
• someone who guides a student

Depending on context, English might translate it as:

• tutor
• mentor
• supervisor
• adviser

So even if the English meaning shown to the learner is different, the Spanish word itself is perfectly natural.

Because Antes de enviar el informe is an introductory time phrase placed at the beginning of the sentence.

Spanish often uses a comma after a fronted introductory phrase, especially when it is a bit longer:

• Antes de enviar el informe, reviso el borrador...

This comma helps readability and marks a pause.

You may also see short introductory phrases without a comma in informal writing, but here the comma is standard and natural.

Yes. Spanish word order is flexible.

You could also say:

• Reviso el borrador con mi tutora antes de enviar el informe.

This means the same thing.

The version with Antes de enviar el informe at the beginning gives more emphasis to the timing:

• Before sending the report, ...

The version with it at the end sounds a little more neutral:

• I review the draft with my supervisor before sending the report.

Both are correct.

It can mean either, depending on context.

Revisar often means:

• to review
• to check
• to go over
• to inspect

In this sentence, it suggests looking over the draft carefully before sending the final report.

So possible English translations include:

• I review the draft
• I check the draft
• I go over the draft

All are reasonable, though review is probably the closest in a formal or academic context.