"मैं दिल्ली आऊँगी ।"

Translation: I will come to Delhi.

[Sean_Roy]

"I shall come to Delhi" is equally valid, but not accepted at this time by Duolingo. In fact, shall used to be considered the correct, non-emphatic future auxiliary verb used with first person subjects, while will was used for second and third person subjects. The emphatic future auxiliary verbs are reversed: will for first person and shall for second and third persons. Hardly anyone knows this these days, however. Nevertheless, the use of shall is still correct.

[Ccf-Uk]

Why are there so many different forms of “Will come” and “Will go”? I know there are different conjugation forms, but teaching so many is a bit much I think.

[Ashwin323375]

What is the difference between "aaoonga" and "aayega"

[vinay92]

आऊँगा (masculine) and आऊँगी (feminine) are the first-person forms. They are conjugated with मैं.

आएगा (masculine) and आएगी (feminine) are the third-person singular forms. They are conjugated with यह, वह and nouns.

[Naxray]

So if I am correct, the letter ऊ in the middle of a future tense verb is used when talking about yourself?

[vinay92]

Yes. You're right.

I've listed the future tense conjugations in my comment on this thread which you can have a look at.