क्या आप शाम को तैयार रहेंगी?

At the beginning of a sentence, क्या usually marks a yes/no question.

So:

• आप शाम को तैयार रहेंगी। = You will be ready in the evening.
• क्या आप शाम को तैयार रहेंगी? = Will you be ready in the evening?

It does not mean what here.
Hindi क्या can mean what, but in this position it functions like a question marker.

आप is the polite/formal way to say you in Hindi.

Comparison:

• तू = very informal/intimate, sometimes rude in the wrong context
• तुम = informal but common and friendly
• आप = polite, respectful, or formal

So this sentence is speaking respectfully to the other person:

• क्या आप शाम को तैयार रहेंगी? = Will you be ready in the evening?

If speaking to a friend informally, you might say:

• क्या तुम शाम ko तैयार रहोगी/रहोगे?

शाम means evening.
शाम को means in the evening or by evening, depending on context.

The word को is often used with times and parts of the day in Hindi.

Examples:

• सुबह को = in the morning
• शाम को = in the evening
• रात को = at night

In English, we use prepositions like in, at, or on.
In Hindi, को often helps express that time relationship.

तैयार means ready, prepared, or set.

In this sentence, it describes the person being spoken to:

• तैयार = ready

So तैयार रहेंगी means something like:

• will be ready
• will stay ready
• will remain ready

A useful point: तैयार behaves like an adjective here.

Great question. रहेंगी comes from रहना, which means to stay, to remain, or sometimes simply helps express a continuing state.

So:

• तैयार रहेंगी = will remain/be ready
• तैयार होंगी = will be ready

In many real situations, both can be possible, but the nuance is a little different:

• होंगी focuses more on the state being ready
• रहेंगी can suggest staying ready or remaining in that ready state

So this sentence can sound a bit like:

• Will you be ready in the evening?
• or Will you stay ready by the evening?

In everyday translation, English usually just says Will you be ready in the evening?

रहेंगी is the future tense form, and it agrees with a female addressee when using polite आप.

Breakdown:

• रह- = verb stem from रहना
• -ेंगी = future ending used here for feminine polite/plural agreement

So:

• क्या आप शाम को तैयार रहेंगी? = said to a woman politely
• क्या आप शाम को तैयार रहेंगे? = said to a man politely, or gender-neutral in many contexts

This is one of the things English speakers often notice:
Hindi verbs can show gender even when the subject is you.

Yes. The form रहेंगी strongly suggests that the speaker is addressing a woman respectfully.

Compare:

• रहेंगी = feminine polite
• रहेंगे = masculine polite / mixed / sometimes default polite

So if you are speaking respectfully to:

• a woman: क्या आप शाम को तैयार रहेंगी?
• a man: क्या आप शाम को तैयार रहेंगे?

No. तैयार stays the same.

Unlike many Hindi adjectives, तैयार does not change here for masculine/feminine or singular/plural in normal use.

So you can have:

• वह तैयार है।
• वह तैयार है।
• वे तैयार हैं।
• आप तैयार रहेंगी।

The agreement shows up mainly in the verb, not in तैयार.

Very literally, it is something like:

• क्या = question marker
• आप = you (polite)
• शाम को = in the evening
• तैयार = ready
• रहेंगी = will remain/be

So a literal translation would be:

• Will you remain ready in the evening?

But natural English is usually:

• Will you be ready in the evening?

Yes, Hindi word order is somewhat flexible, though some orders sound more natural than others.

The standard order here is:

• क्या आप शाम को तैयार रहेंगी?

You may also hear:

• आप शाम को तैयार रहेंगी क्या?
  This is more conversational and puts the question feeling at the end.

• शाम को आप तैयार रहेंगी?
  This gives more emphasis to in the evening.

So the exact word order can shift a little, but the original version is perfectly normal and clear.