have/has + past participle (helped, worked)
We use the present perfect to talk about an action that happened in the past (at any point in time) before now and the action is happening until now, or the action started at one point in the past and finished at another point in the past that is not now. Thus we cannot use specific time adverbs or expressions with the present perfect, such as; last week, yesterday, Friday, Tuesday, last year etc. For these specific time expressions, we MUST use the past simple and NOT the present perfect.
We CAN use time expressions/adverbs that denote an unspecified amount of time with the present perfect, such as; yet, still, ever, never, before, as of now, etc.
Have you ever been to London?
She hasn’t sailed to the far east yet.
Have you responded to my email yet?
I have grown up with three little sisters.
We have worked here for three years.
We use the present perfect to talk about an experience.
I have met the queen herself.
She has six years of work experience in the industry.
Have you ever been to Spain?
We can use the present perfect to talk about achievements. You need not use a reference to a specific time.
I have already passed the test.
Man has walked on the moon.
She has learnt/learned to ride a bicycle.
We use the present perfect to talk about something or a situation that changes or modifies itself over time.
Her English has really improved over these last two years.
They have become super interested in economics.
Have you improved on your football skills since I’ve been away?
Note, it is very common to use time expressions or adverbs of time with the present perfect. Adverbs such as; still, yet, ever, once, several times, etc. Remember, NEVER use time expressions that reference a specific point in time, such as; 1982, yesterday, 17:00h, last week, etc.. Only use the latter expressions with the past simple to signal an action that happened at one point in the past.