Le pneu avant est dégonflé, alors je vais prendre le bus.

In French, many descriptive adjectives come after the noun. Here avant means front and follows pneu:

le pneu avant = the front tire

French often does this with location-type adjectives in similar expressions:

• la roue arrière = the rear wheel
• la porte avant = the front door

So this word order is normal.

Dégonflé means deflated. With a tire, the most natural English translation is often flat.

It comes from the verb dégonfler, meaning to deflate. So:

Le pneu est dégonflé
= The tire is deflated / flat

In this sentence, it mainly describes a state: the tire is flat.

French often uses être + past participle to describe a condition:

• La porte est fermée = The door is closed
• Le pneu est dégonflé = The tire is flat/deflated

So even though dégonflé comes from a verb, here it functions very much like an adjective.

Because it agrees with pneu, which is masculine singular.

So:

• le pneu est dégonflé

If the noun were feminine singular, you would write:

• la roue est dégonflée

If it were plural:

• les pneus sont dégonflés
• les roues sont dégonflées

This is normal adjective agreement in French.

Here alors means so, therefore, or as a result.

It connects the two ideas:

• the front tire is flat
• so I’m going to take the bus

In other contexts, alors can also mean then, but in this sentence so is the best match.

Je vais prendre is the near future form. It means I’m going to take.

Comparison:

• je prends le bus = I take / I’m taking the bus
• je vais prendre le bus = I’m going to take the bus
• je prendrai le bus = I will take the bus

All three are possible in the right context, but je vais prendre is especially common in everyday spoken French when talking about a plan or immediate decision.

In French, prendre is the standard verb for using transportation:

• prendre le bus
• prendre le train
• prendre le métro
• prendre un taxi

Literally, prendre means to take, but in these expressions it corresponds to English take, ride, or go by, depending on context.

French often uses the definite article in general transportation expressions:

• prendre le bus
• prendre le train
• prendre la voiture

This does not always mean one specific bus in the same way English the bus often does. It is simply the normal French expression for that mode of transport.

If you say prendre un bus, it sounds more like taking a bus, one bus among others, often with a more specific or contrastive idea.

Yes. Mon pneu avant est dégonflé means my front tire is flat.

Using le instead of mon can sound natural when the context already makes it clear whose tire you mean. French often uses the definite article where English would sometimes prefer a possessive.

So both are possible, but they do not emphasize the same thing:

• Le pneu avant... = the front tire
• Mon pneu avant... = my front tire

Pneu is a difficult word for many English speakers. It is pronounced approximately /pnø/.

A few key points:

• The p is pronounced.
• The eu sound is like the vowel in deux or bleu.
• Try not to insert an extra vowel between p and n.

So the word starts with a tight consonant cluster: pn-.

Yes. Some common alternatives are:

• donc = so / therefore
• du coup = so / as a result, more informal
• c’est pourquoi = that’s why, more formal

For example:

• Le pneu avant est dégonflé, donc je vais prendre le bus.

Your original sentence with alors is completely natural.