An interrogative sentence is a sentence in a question form. It requires a question mark.
Is this my book?
Did you come yesterday?
If the finite verb is an auxiliary, invert the subject and that auxiliary, or drag the auxiliary to the beginning of the sentence.
She is writing a letter. (Affirmative)
Is she writing a letter? (Interrogative)a

Amie will talk to him. (Affirmative)
Will Amie talk to him? (Interrogative) a

If the finite verb is not an auxiliary, we have to provide an auxiliary from the verb DO. So do, does, or did becomes our new auxiliary verb. But they must appear in the same tense.
She wrote a letter.
She did write a letter.
Did she write a letter? a

She comes here every day.
She does come here every day.
Does she come here every day? a

She came here last week.
She did come here last week
Did she come here last week? a
He drives a car. He drove a car.
Does he drive a car?a Did he drive a car?
Change to interrogative form:
1.Our friends at Koribundu are here.
2. My brother at Fourah Bay College knows the correct answer.
3. Twenty people gathered here yesterday.
4. The man in the blue shirt was nervous.
5. My favourite musician was S.E. Rogers.
6. He went to Mambolo to buy fish.

NEGATIVE
The negative is even simpler to build. Remember that the negative signal is not , or n't placed immediately after the auxiliary verb. But the n't is completely welded to the auxiliary verb, with no space allowed.
She is writing a letter.
She is not writing a letter.
She isn't writing a letter.
If the finite verb is not an auxiliary, a member of the verb DO (e.g. do, does, did) may be used as auxiliary, and the not or n't is then applied as we've done above.
She likes the village.
She does not like the village.
She doesn't like the village.
I know the way. I don't know the way
He wrote the letter. He didn't write the letter.
He comes here every day
He doesn't come here every day.