Please tell me how to whiten my skin.

I'm worried about my darkened skin after traveling abroad. I've been researching various methods for whitening my skin, but I feel like recovery is slow with just regular whitening treatments. I'd like to know which specialized treatments are particularly effective for whitening my skin, among those available at hospitals. If possible, I'd like to consult about a more effective skin whitening method, such as laser or whitening treatments.