Can you tell me how long does concussion last?

Few weeks to a year. Some people will have concussion resolve within a few hours. However, for many symptoms will last for several weeks, months to as long as a year.
Usually resolve. A concussion is an event of momentary trauma to your brain. The effects afterwards usually resolve for most people within 1-3 months, depending on predisposing factors, number of prior concussions, severity, and medical management (including how well you follow the guidelines). In most cases, the more you rest, the more your brain can heal and symptoms will resolve.
RECOVERY VARIES. To concus means 'to shake violently'; which is what happens to the brain when the head or trunk is violently impacted. This violent event causes brain injury at the cellular level, which is why symptoms and recovery are vary from person to person. The key to recovery is close follow up with a provider knowledgeable in the concussion who'll monitor symptoms & neurocognitive test results.