Usages of за
Мы подошли к стойке регистрации за два часа до вылета.
We came to the check-in desk two hours before departure.
За час до вебинара я проверю микрофон и камеру.
An hour before the webinar, I will check the microphone and the camera.
Elon.io is an online learning platform
We have an entire course teaching Russian grammar and vocabulary.