Video narration
How do you talk about studying that started earlier and is still happening now? Say, "I've been studying": have or has, then been, then a verb ending in -ing. Use have with I, you, we, and they; use has with he, she, or it. Your study session began earlier and is still going now. That's the shift: not an isolated past action, but an earlier activity connected to now. Even if you've just stopped, tiredness from studying connects that activity to now. For and since are common additions: for two hours, or since breakfast, but neither is required. This tense often focuses on the studying itself, or how long it's been going on. For the result, "I've finished reviewing" puts completion first. So, for your study session, say, "I've been studying." It began earlier and is still happening now.