How much time does an athlete have for each trial?

Under the World Athletics Technical Rules, the time starts when the responsible official indicates that all is ready (for the pole vault, when the crossbar has been adjusted to the athlete's previous wishes). If the time elapses after the athlete has started the trial, the trial is not disallowed. If the athlete decides not to attempt the trial, it is a failure once the allowed period elapses.

Individual events:

• More than 3 athletes remaining (or the very first trial of each athlete): 1 minute for high jump, pole vault and other events.
• 2 or 3 athletes: high jump 1.5 minutes, pole vault 2 minutes, other events 1 minute.
• 1 athlete: high jump 3 minutes, pole vault 5 minutes.

Combined events: the same, except with 1 athlete remaining it is 2 minutes for high jump and 3 minutes for pole vault.

If the time is exceeded the trial is recorded as a failure, unless a determination is made under Rule 25.18.

Source: https://worldathletics.org/about-iaaf/documents/book-of-rules (Technical Rules, time allowed for trials)