There is a very big difference between must not and don’t have to. “Must not” is like DO NOT! But “don’t have to” often means you can if you want, but it’s not necessary. Here are some examples:

You must not touch the hot stove.
You must not wake me up in the morning! I will be very cranky!
You must not drink milk that has expired.

You don’t have to wear a raincoat today, it’s not supposed to rain.
You don’t have to eat all your broccoli, it doesn’t taste very good.
You don’t have to go to school today because it’s a holiday.

Do you see the difference? “Must not” is more like a command, but “don’t have to” lets the listeners decide or conclude they do not need to do something.

What is a Gerund (sounds like “Jer-und”)? Simply put, it is a verb + ing while acting like a noun in a sentence. Also, it can be the object in a sentence. Here are a few examples:

Swimming is fun. ✔️

Here, swimming is the gerund. It’s acting like a noun – “swimming is…” Now look at this sentence:

I like swimming. 🏊

Is swimming the gerund here? No, because it’s not acting like a noun. It’s doing its job as a verb.

One more thing to remember about Gerunds: Gerunds are used after prepositions. Remember, prepositions explain “where.” Here are a few examples:

She has an interest in becoming a swimmer.

You shouldn’t be a life guard if you are afraid of swimming.

I commend you for practicing so much.

In the above examples, the pattern is

[noun/pronoun/verb/adjective] + [conjunction] + [gerund]

So what do you need to remember about gerunds? They are verbs acting like nouns, with + ing. Also, they can be the object in a sentence.