FOR / SINCE – a mixture of past and present: “have been doing”

In English, you really need to think about where you are placed in time, all the time! When you describe an action in the past, you need to construct your phrase differently based on whether the exact date is mentioned or not.
(You can review this topic here)
IN SOME CASES, YOUR PHRASE IS BOTH IN THE PRESENT AND IN THE PAST

How is it possible? Look at the following phrases – they all mention Megan, a singer, who also loves guitar. What is the right way to connect the Subject (Megan) and the action?

“Megan (play) guitar every day”. Is the phrase in the present or in the past?

The phrase is in the Present: “Megan plays guitar every day”.

“Megan (play) guitar right now”. Present or past?

The phrase is in the Present (Active Present – action happenning at the exact present moment) : “Megan is playing guitar right now”.

“Megan (play) guitar in a concert with her band last month”. Present or past?

The phrase is in the Past because a specific date in the past (“last month”) is mentioned : “Megan played guitar in a concert with her band last month.”

“Megan (play) guitar at different birthday parties about a hundred times in her life”. Present or past?

The phrase is in the Past (non-specific Past) because it describes Megan’s past experiences, but doesn’t mention a date when it happened exactly : “Megan has played guitar at different birthday parties about a hundred times in her life”.

Megan (play) guitar for twenty years. Present or past?

Present or past?

The phrase is BOTH in the Present (because Megan plays guitar today) AND the PAST (because the past period of twenty years is indicated). “Megan has been playing guitar for twenty years”.

HOW TO CONSTRUCT A PHRASE IN THE PRESENT AND IN THE PAST :
HAVE (shows the past) + been “doing” (shows the present)

You need to use this form under two conditions:
1. The situation is true today.
2. The phrase contains “FOR” + a period of time or SINCE + the starting point in time

For the phrases below, decide if “have been doing” can be appropriate in each case and why:

Megan started learning Japanese two years ago, and she is still doing it.

You can make one phrase out of these two separate phrases by saying “Megan has been learning Japanese for two years.”

Megan constantly checks out all the song albums that get released by new artists.

The phrase is in the Present, and no indication of any past actions or time periods is mentioned.

Megan studied drawing some years ago, but then she stopped.

The phrase is entirely in the Past and has no connection to the Present anymore.

Megan decided to design her own stage costumes five years ago, and it is still the case today.

You can make one phrase out of these two separate phrases by saying “Megan has been designing her own stage costumes for five years.”

CAREFUL: In some cases, when the action is in the Present without “FOR/SINCE”, but you want to underline its intensity and duration, “have been doing” can also be used. Examples:

Could you stop playing the drums for one second? I’ve been listening to them all day, and I’m sick of them!

Where have you been? Why didn’t you come sooner? I’ve been waiting for you!

I’ve been watching you, and I can see that you are going through a difficult time in your life.

I can tell you all about how crypto currency works. I’ve been reading a lot on this topic.