Tafadhali simama darasani na ujibu swali hili.

Yes. Tafadhali is the usual polite word for please.

In this sentence, it makes the command sound polite:

• Tafadhali simama... = Please stand...

You can often place tafadhali at the beginning or end of a request:

• Tafadhali simama.
• Simama, tafadhali.

Both are polite.

Because in Swahili, commands usually do not need an explicit subject.

So:

• simama already means stand / stand up! addressed to one person
• there is no need to add a word for you

This is similar to English imperatives:

• Stand up!
• not usually You stand up!

Simama means stand or stand up.

In context, it usually means stand up, especially if the person is sitting. Swahili often uses the same verb where English might choose either stand or stand up, depending on the situation.

So here it most naturally means:

• Please stand up...

Darasani means in the classroom or in class.

It comes from:

• darasa = class / classroom
• -ni = a locative ending meaning something like in / at / to

So:

• darasa → darasani
• in class / in the classroom

This -ni ending is very common in Swahili:

• nyumbani = at home
• shuleni = at school
• mezani = on the table / at the table

This is a very common learner question.

After one command, Swahili often uses na plus the subjunctive form for the next action:

• simama ... na ujibu ...

Here, ujibu means something like:

• and answer
• and then answer

A simple direct command by itself would be:

• Jibu swali hili. = Answer this question.

But when it is linked after another command, na ujibu sounds natural and correct.

Yes, na usually means and.

In this sentence, it links two actions:

• simama = stand up
• ujibu = answer

So:

• simama darasani na ujibu swali hili
• stand up in class and answer this question

Depending on context, na here can feel like and or and then.

Because in Swahili, demonstratives like this usually come after the noun.

So:

• swali hili = this question
• literally: question this

This word order is normal in Swahili:

• kitabu hiki = this book
• mtoto huyu = this child
• watu hawa = these people

So English and Swahili are different here:

• English: this question
• Swahili: question this

Yes:

• Tafadhali = please
• simama = stand / stand up
• darasani = in class / in the classroom
• na = and
• ujibu = answer
• swali hili = this question

A natural full translation is:

• Please stand up in class and answer this question.

You would change the command forms to plural.

One natural plural version is:

• Tafadhali simameni darasani na mjibu swali hili.

Here:

• simameni = stand up! (to more than one person)
• mjibu = answer! (to more than one person, in this linked-command pattern)

So singular vs. plural is:

• simama ... na ujibu ... = to one person
• simameni ... na mjibu ... = to several people

Not always.

It can mean:

• in the classroom
• in class
• sometimes more generally during class, depending on context

So the exact English translation can change slightly:

• Please stand up in the classroom...
• Please stand up in class...

Both can fit darasani.

A helpful approximate pronunciation is:

ta-fa-dha-li

The dh sound is like the th in this, not the th in thin.

So it sounds roughly like:

• ta-fa-tha-li
  with a voiced th sound.

Also, Swahili pronunciation is usually quite regular: words are generally pronounced the way they are written.