يخلي الفريق المبنى ويطفئ النار.

Because Arabic often prefers verb–subject–object order in simple statements. So يُخلي الفريقُ المبنى is a very normal MSA pattern.

You can also say الفريقُ يُخلي المبنى. That is also correct, but it gives a little more emphasis to the team.

Without short vowels, Arabic spelling can be ambiguous. In formal MSA, this is most naturally read as يُخلي from أخلى, meaning to evacuate / clear out.

A colloquial form يخلّي can mean things like lets, makes, or leaves, depending on dialect. In a formal sentence like this, the intended MSA reading is normally يُخلي.

Because فريق is grammatically a singular noun meaning team. Arabic agrees with the grammatical form of the noun, not with the number of people inside the group.

So الفريق takes a singular masculine verb here: يُخلي الفريقُ
not because only one person acts, but because team is singular.

Because يُخلي is a transitive verb in this meaning. The thing being evacuated or cleared is its direct object.

So Arabic says: يُخلي الفريقُ المبنى just as English can say the team evacuates the building.

That final letter is alif maqṣūra: ى. It usually sounds like a long ā sound, not like y.

So المبنى is pronounced roughly al-mabnā. This is just the normal spelling of this noun in Arabic.

It also means that case endings are not visibly written on the end of this word.

It is pronounced roughly yuṭfiʾu.

The difficult part is the final hamza ء. After yuṭfi-, you make a brief stop in the throat: yuṭfiʾu.

This verb comes from أطفأ, meaning to extinguish / put out.

Because ن is a sun letter. With sun letters, the ل of ال is not pronounced, and the next consonant is doubled in pronunciation.

So:

• written: النار
• pronounced: an-nār

The spelling stays the same, but the sound changes.

Not necessarily. They are in the Arabic imperfect form, which can express:

• present action
• habitual action
• near future
• narrative present

So depending on context, they could mean something like evacuates, is evacuating, or even will evacuate.

Because Arabic, like English, often leaves out a repeated subject when it is still the same.

So: يُخلي الفريقُ المبنى ويُطفئ النار means that the team does both actions.

If Arabic wanted to introduce a different subject for the second verb, it would normally state it.

In normal Arabic writing, short vowels and case endings are usually omitted.

In a fully vocalized version, you would expect something like: يُخلي الفريقُ المبنى ويُطفئ النارَ

Here:

• الفريقُ is the subject, so it is nominative
• النارَ is a direct object, so it is accusative
• المبنى is also a direct object, but because it ends in ى, its case ending is not visibly shown

So the grammar is still there, even when the ordinary spelling does not show all of it.