Present perfect: before, have & ever

We use the present perfect to talk about general experiences in the past. The main point to note is that we don’t mention a time and don’t give any detail. Key words here are ever and before.

We form the present perfect with the verb to have and the past participle of the main verb.

I have worked in London.
She has been to Milan.
We have given a presentation.

Negatives are formed with not.
I have not worked in London before.
She has not been to Milan before.
We have not given a presentation before.

Questions are formed by inverting the subject and verb to have.
Have you worked in London before?
Has she been to Milan before?
Have they given a presentation before?

The following short forms are used in speech and informal writing:
I have – I’ve
you have – you’ve
he has – he’s
she has – she’s
it has – it’s
we have – we’ve
you have – you’ve
they have – they’ve