Brandtrappen og redningsåbningen er bag bygningen.

Because -en is the usual definite singular ending for common-gender nouns in Danish. It works like English the.

So:

• brandtrappe → brandtrappen
• redningsåbning → redningsåbningen
• bygning → bygningen

In other words, Danish often puts the onto the end of the noun instead of using a separate word in front.

It is singular.

Even though the whole subject refers to two things together:

• brandtrappen = the fire escape
• redningsåbningen = the rescue opening

each noun is still singular by itself.

Some useful forms:

• brandtrappe = a fire escape
• brandtrappen = the fire escape
• brandtrapper = fire escapes
• brandtrapperne = the fire escapes

The same pattern applies to the other nouns too.

Because in a simple noun phrase, Danish normally uses only the ending for definiteness, not a separate word plus the ending.

So you say:

• bygningen = the building

not:

• den bygningen

However, when there is an adjective, Danish often uses both:

• den store bygning = the big building

So in this sentence, since the nouns stand alone without adjectives, the ending -en is enough.

Yes. Danish uses compound nouns very often, and they are usually written as one word.

Here they break down like this:

• brandtrappe = brand
  • trappe
• redningsåbning = redning
  • s
    • åbning

This is very common in Danish. English sometimes writes similar ideas as two words, but Danish often joins them into one.

That -s- is a linking element used in some compounds. It does not mean possession here.

So redningsåbning is not the same as English rescue’s opening. It is just one compound noun meaning an opening used for rescue.

You will see this kind of linking s in many Danish compounds. Sometimes it appears, sometimes it does not, and learners usually just have to get used to the most common patterns word by word.

Because Danish verbs do not change form for singular and plural in the present tense.

So:

• bygningen er... = the building is...
• brandtrappen og redningsåbningen er... = the fire escape and the rescue opening are...

In English, we change is to are. In Danish, the verb stays er.

Because bag is the preposition meaning behind.

So:

• bag bygningen = behind the building

This is the normal way to express location here.

You may also come across bagved, which can sometimes be used in similar contexts, but bag bygningen is a very natural and standard way to say it in this sentence.

The sentence follows a very normal Danish main-clause pattern:

• Brandtrappen og redningsåbningen = subject
• er = verb
• bag bygningen = place expression

So the structure is:

subject + verb + location

If you move the location to the front, Danish keeps the verb in second position:

• Bag bygningen er brandtrappen og redningsåbningen.

That verb-second pattern is an important feature of Danish word order.

Two sounds that often feel difficult for English speakers are:

• y in bygningen
• å in redningsåbningen

A rough guide:

• y is a front rounded vowel. A useful trick is to try saying an ee sound while rounding your lips.
• å is roughly like the vowel in law or saw for many English speakers.

Also, the ending -en is often pronounced lightly in normal speech.

And in compounds, the main stress is usually on the first part:

• BRANDtrappen
• REDningsåbningen
• BYGningen

These are only rough guides, but they can help you get closer to a natural pronunciation.