English’s preterite — usually called its simple past or, somewhat loosely, its past-tense form — is generally formed by adding -ed or -d to the verb’s plain form (bare infinitive), sometimes with some spelling modifications:

He planted corn and oats.

They studied grammar.

ex:

We have lived in this city for 20 years. (No we are moving to another city.)

2. Present perfect tense is also used to express an action that happened at cetain time in the past but its result is still is there.

Ex:

Who has eaten the biscuits? (the box is empty now)

The simple past tense is used to express an action that happend in the past.

Ex: He moved to Paris last year.

In a ‘perfect’ tense you have a main verb in a past tense form and the auxilliary verb ‘to have’. Don’t ask why that makes it ‘perfect.’

In phrases like ‘present perfect’, ‘past perfect’, ‘future perfect’ the thing that’s in the present/past/future is the AUXILLIARY VERB, not the main one, which is always in the past tense form.

Example:

Simple present: I eat eggs.

Simple past: I ate eggs.

Simple future. I will eat eggs.

Present perfect. I HAVE eaten eggs.

Past perfect. I HAD eaten eggs

Future perfect I WILL HAVE eaten eggs.

n in past simple u just use the V3 form of the verb

I have worked here for years.

or

I have been working here for years.

Past simple:

I worked there for years.

.