Se tiveres tempo, ajuda-me a enxugar a loiça enquanto eu guardo os pratos.

Because Portuguese often uses the future subjunctive after se when talking about a possible future situation.

So:

• se tiveres tempo = if you have time / if you happen to have time
• se tens tempo = more like if you have time as a current or general fact

In this sentence, the speaker is making a request that depends on whether the other person has time, so se tiveres tempo is the natural choice.

Tiveres is the tu form of the future subjunctive of the verb ter (to have).

The future subjunctive of ter is:

• eu/ele/ela/você tiver
• tu tiveres
• nós tivermos
• vós tiverdes
• eles/elas/vocês tiverem

So se tiveres tempo literally means if you have time when speaking to tu.

Yes. In Portuguese, subject pronouns are often omitted because the verb ending already shows who the subject is.

Here, the clues are:

• tiveres → tu
• ajuda → affirmative imperative for tu

So the full idea is:

• Se tu tiveres tempo, ajuda-me...

But saying tu is unnecessary unless you want emphasis.

Grammatically, yes: ajuda-me is an affirmative imperative form, so it is technically a command.

But in real use, it can sound like a normal request, not rude at all, especially because the sentence begins with:

• Se tiveres tempo = If you have time

That softens it. So the overall tone is more like:

• If you have time, help me...

rather than a harsh order.

In standard European Portuguese, affirmative commands usually put the object pronoun after the verb, joined with a hyphen:

• ajuda-me
• diz-me
• leva-o

This is called enclisis.

So in Portugal, ajuda-me is the standard form here.
Me ajuda is much more associated with Brazilian Portuguese.

Because in Portuguese, when a clitic pronoun like me, te, lhe, o, a, etc. comes after the verb, it is normally attached with a hyphen.

So:

• ajuda-me
• lava-o
• diz-lhe

The hyphen is not optional here; it is part of the correct spelling.

After ajudar, European Portuguese very commonly uses a + infinitive to express the action someone is helping with:

• ajudar alguém a fazer algo = to help someone do something

So:

• ajuda-me a enxugar a loiça = help me dry the dishes

Without a, you may sometimes hear similar structures, but ajudar alguém a + infinitive is very natural and standard in Portugal.

Here, enxugar means to wipe dry or to towel-dry.

That makes it a very natural verb for dishes, because after washing them, you often dry them with a cloth.

• enxugar a loiça = wipe/dry the dishes
• secar = dry in a more general sense

So secar is not wrong in every context, but enxugar is especially good when you mean drying by wiping.

That is a very common point of confusion because of regional differences.

• In European Portuguese, loiça is the normal word.
• In Brazilian Portuguese, you will usually see louça.

They refer to the same general idea: dishes, crockery, tableware.

So for Portuguese from Portugal, loiça is exactly what you would expect here.

Not exactly.

• loiça is a collective/general word: dishes, crockery, tableware
• pratos means specifically plates

So the sentence separates two tasks:

• ajuda-me a enxugar a loiça = help me dry the dishes in general
• enquanto eu guardo os pratos = while I put away the plates

That is perfectly natural. The speaker is talking broadly in one part and specifically in the other.

Yes, it could.

Portuguese often omits subject pronouns, so:

• enquanto guardo os pratos

would also be correct.

The eu is included here for a bit more clarity or contrast, as if saying:

• you do this, while I do that

So eu is not required, but it adds emphasis.

No. In this context, guardar means to put away or to store.

So:

• guardar os pratos = put the plates away
  (for example, back into a cupboard)

This is a very common household use of guardar in Portuguese.

You would change the verb forms to match você:

• Se tiver tempo, ajude-me a enxugar a loiça enquanto eu guardo os pratos.

Main changes:

• tiveres → tiver
• ajuda-me → ajude-me

This version is more formal or more distant than the original tu version.