På skjemaet må du skrive både fornavn, etternavn og fødselsdato tydelig.

In Norwegian, på skjemaet is the normal way to say on the form when you mean writing information in the spaces provided on a form.

• på = on
• skjemaet = the form

Even though in English we might sometimes think of writing in a form, Norwegian usually uses på here.

Examples:

• Skriv adressen på skjemaet. = Write the address on the form.
• Det står på skjemaet. = It is written on the form.

Skjemaet is the definite form of skjema, meaning the form.

• et skjema = a form
• skjemaet = the form

Norwegian often adds the definite article as an ending on the noun instead of using a separate word like the.

So:

• på skjemaet = on the form
• på et skjema = on a form

Yes. må is the present tense form of the modal verb måtte, and here it means must or have to.

• du må skrive = you must write / you have to write

In this sentence, må du skrive appears after på skjemaet, but the meaning is still the same.

A few examples:

• Du må vente. = You must wait.
• Du må fylle ut skjemaet. = You must fill out the form.

Because Norwegian follows the verb-second rule in main clauses. This means the finite verb usually comes in the second position.

If you start with På skjemaet, then the verb must come next:

• På skjemaet må du skrive ...

If you start with the subject, then you get:

• Du må skrive ... på skjemaet

Both are correct, but they have slightly different emphasis:

• På skjemaet må du skrive ... emphasizes on the form
• Du må skrive ... på skjemaet is more neutral

Både ... og ... means both ... and ..., but in Norwegian it can also be used when listing more than two things, as in this sentence.

Here:

• både fornavn, etternavn og fødselsdato = both first name, surname, and date of birth

It signals that all of these items must be included.

Examples:

• Hun liker både te og kaffe. = She likes both tea and coffee.
• Du må oppgi både navn, adresse og telefonnummer. = You must give name, address, and phone number.

Because these words are being used in a general, category-like way, similar to labels on a form.

So:

• skrive fornavn, etternavn og fødselsdato = write first name, surname, and date of birth

This is very common in instructions and lists. English often does something similar:

• Write name, address, and phone number

You could sometimes see articles in other contexts, but here they are not needed.

That comma separates items in a list:

• fornavn, etternavn og fødselsdato

This is just like English punctuation in a simple list. Norwegian usually does not put a comma before og in an ordinary list.

So this is normal:

• A, B og C

Tydelig means clearly or legibly here.

It comes from the adjective tydelig, meaning clear or distinct, but in this sentence it functions adverbially, describing how you should write.

So:

• skrive tydelig = write clearly / write legibly

Examples:

• Snakk tydelig. = Speak clearly.
• Du må skrive tydelig. = You must write clearly.

That is a very normal position in Norwegian. Adverbs that describe the manner of an action often come after the main verb phrase or after the object.

So:

• Du må skrive tydelig.
• Du må skrive navnet tydelig.

In this sentence, tydelig describes the whole writing action, so putting it at the end sounds natural.

Exactly. Norwegian very often combines nouns into one word.

• fødsel = birth
• dato = date
• fødselsdato = date of birth

The -s- in the middle is very common in compounds.

Other similar examples:

• telefonnummer = telephone number
• etternavn = surname
• personnummer = personal identity number

This is something English speakers need to get used to, because English often writes these as separate words.

Sometimes, but not always. Navn just means name, and it can be less precise.

On a form, fornavn and etternavn are often separated because they must be written in different fields:

• fornavn = first name / given name
• etternavn = surname / family name

So in this sentence, using both words is more exact and more typical for form instructions.

Usually yes, but a more exact translation is often given name.

That matters because first name works well in many cases, but naming systems differ between cultures. Fornavn refers to the personal name you are given, while etternavn refers to the family name or surname.

So:

• fornavn = given name / first name
• etternavn = surname / last name / family name

A very natural alternative would be:

• Du må skrive både fornavn, etternavn og fødselsdato tydelig på skjemaet.

This has the same basic meaning. The original sentence puts På skjemaet first to foreground the place where the information must be written. That style is common in instructions.