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According to https://englishsentences.com/present-tense/

b. Present Continuous

The present continuous tense describes actions
and/or events that are currently happening or going on now; in other
words, things that are continuing to happen right now in “real time.”

and

d. Present Perfect Continuous
The present perfect continuous expresses
actions (or events) that we have been doing and are still doing;
things that have been going on and are still going on now.

My question is that, in some situations, can these both tenses represent the same timeline ?

For Example

1. He is taking the exam for last 2 hours - Present Continuous ???




2. He has been taking that exam for at least 2 hours - Present Perfect Continuous.

Don't the above two sentences tell us the same thing ? Or is the 1st sentence grammatically incorrect ?

What am I missing ?

Thanks.

Q: Can Present Perfect Continuous and Present Continuous have the same meaning?

Yes, there are often times when there is very little difference between the two, and they pretty much mean the same thing. However, your example is not a very good one.

Native speakers would not say:

He is taking the exam for the last 2 hours.

The problem with that sentence is the time reference back toward the past. We don’t use the present continuous is a context like that. Although we might say:

He is taking the exam for the next 2 hours.

to mean that he will be busy for the next two hours taking the exam.

However, we could say:

He is taking the exam in that room.

And also say:

He has been taking the exam in that room.

and those two sentences pretty much mean the same thing. However, the first one could be interpreted in a couple different ways. It could mean:

He is (currently) taking the exam in that room (right now).

but it could also mean:

When it’s time for him to take the exam, he’ll be taking the exam in that room.

The specific meaning would usually be apparent based on the context. For example, am I answering the question:

What is he doing at the moment? (He is taking the exam in that room.)

or did I answer the question:

Where will he take the exam? (He is taking the exam in that room.)

although in the latter case, I think many might be inclined to say one of these instead:

He will take the exam in that room.

He is to take the exam in that room.

The EF website has an interesting note about this:

USING THE PRESENT CONTINUOUS TO TALK ABOUT THE FUTURE

The present continuous is used to talk about arrangements for events at a time later than now. There is a suggestion that more than one person is aware of the event, and that some preparation has already happened.

For example:
I am leaving tomorrow. = I've already bought my train ticket.

I'd like to add that both tenses can be used to express a temporary or new habit, for example:

I have been eating a lot of cakes recently, or I am eating a lot of cakes presently. This means that at the moment (not necessarily now, but these last weeks) I have been eating a lot of cake, which I don't do usually. Maybe I am practicing my baking skills.