Je dois être à l'heure au travail.

Devoir is a modal verb in French that expresses necessity or obligation. When you pair it with another verb, that second verb stays in the infinitive form.
• Je dois = “I have to”
• être = “to be”
Together, Je dois être literally means “I have to be.”

Here is the present‐tense conjugation of devoir:
• Je dois
• Tu dois
• Il/Elle/On doit
• Nous devons
• Vous devez
• Ils/Elles doivent
Just replace je dois with the correct form for tu, il, nous, etc.

Être à l’heure is an idiomatic expression in French.
• être = “to be”
• à l’heure = literally “at the hour,” but idiomatically “on time”
You can’t say être en temps to mean “on time”; the fixed phrase is être à l’heure.

In French, à + le contracts to au.
• à le travail → au travail
This contraction is mandatory for masculine singular nouns introduced by le.

• être à l’heure focuses on being punctual in general—showing up or being ready exactly on time.
• arriver à l’heure emphasizes the act of arriving at the workplace on time.
Both are correct; choose être for a general state of punctuality, arriver for the action of getting there on time.

Yes, but it’s less common.
• au travail (standard expression “at work”)
• à mon travail (literally “at my work”)
Use au travail for a general “at work” idea; use à mon travail if you really want to stress “my workplace.”

Absolutely. In casual conversation, you can say:
• Je dois être à l’heure au boulot.
• Je dois être à l’heure au job.
Boulot and job both mean “work” or “job” but are more colloquial than travail.

Heure begins with a mute h (h muet), so you don’t pronounce it.
• l’heure is pronounced [lœʀ].
Because the h is silent, liaison occurs with preceding words (e.g., à + l’heure → [a.lœʀ]).