Questions & Answers about Сегодня в офисе учебная тревога.
Russian often leaves out to be in the present tense.
So this sentence literally looks like:
- Сегодня — today
- в офисе — in the office
- учебная тревога — a drill / training alarm
But the full sense is something like:
- Today, there is a drill in the office
- Today, the office has a drill
- Today, there’s a practice alarm in the office
In present-tense Russian, you normally do not say есть in this kind of sentence. Using no verb here is completely normal.