Active sentences in the present continuous tense have the following structure:
Subject + is/are/am + -ing form of the verb + object
Passive sentences in the present continuous tense have the following structure:
Object of the active sentence + is/are/am + being + past participle form of the verb + by + subject of the active sentence.

Examples are given below.

Active: I am reading a story.
Passive: A story is being read by me.
Active: The engine is driving the train.
Passive: The train is being driven by the engine.
Active: She is singing a song.
Passive: A song is being sung by her.
Active: The carpenter is making furniture.
Passive: Furniture is being made by the carpenter.

When the verb is followed by a preposition

Read the sentence given below:

My mother is talking to a stranger.
Here the noun a stranger is the object of the preposition to, and not the verb talking. But this sentence can be changed into the passive:

Passive: A stranger is being talked to by my mother.
Active: The children are laughing at the old beggar.
Passive: The old beggar is being laughed at by the children.
Active: I am waiting for him.
Passive: He is being waited for by me.

Changing a negative sentence into the passive

When a negative sentence is changed into the passive, not will come between is/am/are and being.

Active: She is not writing a story.
Passive: A story is not being written by her.

Changing an interrogative sentence into the passive

The passive forms of these sentences will begin with be (is/am/are). When the active sentence begins with a question word such as when, whose, why, which and how, the passive sentence will also begin with a question word. When the active sentence begins with who or whose, the passive sentence will begin with by whom or by whose. When the active sentence begins with whom, the passive sentence will begin with who.

Active: Are the masons building a house?
Passive: Is a house being built by the masons?
Active: Who is waiting for you?
Passive: By whom are you being waited for?
Active: Whom are you waiting for?
Passive: Who is being waited for by you?
Active: Why is he not learning his lessons?
Passive: Why are his lessons not being learnt by him?
Active: Whose father is helping you?
Passive: By whose father are you being helped?