Questions & Answers about Vakten varsler oss hvis døren står åpen.
Both translations are possible, but nuance matters:
- å varsle (noen) = to notify/alert/inform (often neutral/formal).
- å advare (noen) = to warn (about danger or something negative).
In this sentence, Vakten varsler oss most naturally means “The guard notifies/alerts us.” If the focus were on danger, advarer would be more pointed.