1. PRESENT PERFECT Have / has + past participle
To talk about recent completed actions or events that are relevant now.
I have forgotten her name. (I don’t remember it now)
To talk about an indefinite or unspecific time in the past.
People have bought his paintings for millions of dollars.
To talk about experiences up to the present.
He has lived in France for years. (He still lives there.)

2. Present perfect vs. Simple past
Indefinite time in the past.
Justin Beiber has become famous worldwide.
Use for and since to express unfinished past
I have been home since 3 PM.
Specific time in the past
Justin Beiber became famous after his first album release in the year X.
We can express the same ideas in past.
I came home at 3 PM.

3. EVER: to talk about experiences in the time up to now.
Ever=any time
Have you ever wondered what is it like?
We also use it in affirmative statements after superlatives
That is the most exciting thing I have ever done.
Mainly used in questions.
Have you ever gone to the beach?
NEVER: to say something you have never done
Never= at no time
I have never tried that meal.

4. JUST: for very recent events
They´ve just finished their tests.
YET: to show we expect something to happen (write it at the end of the sentence).
I haven´t cooked the dinner yet. Please be patient.
ALREADY: to emphasize that something has happened earlier than expected.
They have already done the project.

5. FOR: unfinished past (for + period of time) to say how long something lasted.
- I have been a teacher for 5 years.
SINCE: unfinished past (since + period of time) to say when something started.
- I have worked since 7:30AM.