मैं जल्दी आऊँगी, और तुम देर नहीं करोगी।

Because both verbs are in the future tense and both agree with a female subject.

• आऊँगी = I will come (said by a female speaker)
• करोगी = you will do / you will be (said to a female तुम)

In Hindi, future forms often show gender:

• मैं आऊँगा = I will come (male speaker)
• मैं आऊँगी = I will come (female speaker)

And with तुम:

• तुम करोगे = you will do (to a male or mixed group, in many contexts)
• तुम करोगी = you will do (to a female)

So the sentence suggests:

• the speaker is female
• the person being addressed is female

Hindi often allows the subject pronoun to be dropped if it is already clear from context.

So both of these are possible:

• मैं जल्दी आऊँगी।
• जल्दी आऊँगी।

The first is more explicit: I will come early.
The second can sound more natural in conversation if it is obvious who is speaking.

Learners often see pronouns more often in teaching sentences because they make the meaning clearer.

आऊँगी is the feminine singular future form of आना (to come) for मैं.

Breakdown:

• आना = to come
• future stem here becomes roughly आऊँ-
• -गी marks feminine singular future

So:

• मैं आऊँगा = I will come (male)
• मैं आऊँगी = I will come (female)

The ँ in आऊँगी shows nasalization. You do not need to overthink it at first; just learn आऊँगा / आऊँगी as standard future forms of आना.

In Hindi, नहीं usually comes before the verb it negates.

So:

• तुम देर नहीं करोगी = you will not be late / you will not delay

This placement is very normal in Hindi:

• मैं नहीं जाऊँगी = I will not go
• वह नहीं आएगा = he will not come
• हम नहीं करेंगे = we will not do

English puts not after an auxiliary (will not do), but Hindi usually puts नहीं before the main verb form.

Yes, literally it is something like to do lateness, but idiomatically it means:

• to be late
• to delay
• to take too long

So:

• तुम देर नहीं करोगी can mean you won’t be late
• depending on context, it can also mean you won’t delay

This is a very common Hindi pattern: a noun + करना makes a verbal expression.

Examples:

• फ़ैसला करना = to make a decision
• कोशिश करना = to try
• देर करना = to delay / be late

Yes, they are near-opposites in this kind of sentence.

• जल्दी = early / quickly / soon
• देर = late / delay

So the sentence creates a natural contrast:

• मैं जल्दी आऊँगी = I will come early
• और तुम देर नहीं करोगी = and you won’t be late / and you won’t delay

A learner should notice that जल्दी is functioning adverbially here, modifying आऊँगी.

और means and.

It simply joins the two clauses:

• मैं जल्दी आऊँगी
• तुम देर नहीं करोगी

So:

• मैं जल्दी आऊँगी, और तुम देर नहीं करोगी। = I will come early, and you won’t be late.

In everyday Hindi, speakers sometimes omit और if the connection is already clear, but including it is completely normal.

The verb endings would change according to gender.

If the speaker is male and the listener is female:

• मैं जल्दी आऊँगा, और तुम देर नहीं करोगी।

If the speaker is female and the listener is male:

• मैं जल्दी आऊँगी, और तुम देर नहीं करोगे।

If both are male:

• मैं जल्दी आऊँगा, और तुम देर नहीं करोगे।

So the endings tell you something about the people involved.

Hindi has different levels of you:

• तू = very intimate / very informal
• तुम = familiar, common
• आप = polite / formal

This sentence uses तुम, so it sounds familiar but not rude.

Compare:

• तू देर नहीं करेगी।
• तुम देर नहीं करोगी।
• आप देर नहीं करेंगी।

All can mean you will not be late, but they differ in register and grammar.

So this sentence is addressed to someone the speaker knows well enough to use तुम with.

The given order is very natural:

• मैं जल्दी आऊँगी, और तुम देर नहीं करोगी।

Hindi word order is often flexible, but not completely free. You may move some adverbs for emphasis, but the standard order here is straightforward.

For example:

• मैं जल्दी आऊँगी is more neutral than मैं आऊँगी जल्दी
• तुम देर नहीं करोगी is the most natural order

For learners, it is best to remember this sentence as a good normal pattern: subject + adverb/object + नहीं (if needed) + verb

It most naturally means you won’t be late or you won’t delay.

The exact English translation depends on context:

• If talking about arrival time: you won’t be late
• If talking about doing something on time: you won’t delay

That is common in Hindi: one expression can map to more than one natural English phrasing.

So even if the meaning has already been shown to you, it is useful to know that देर करना is slightly broader than just one fixed English translation.