Compare the past form and be -ing

We use the past form for finished actions. They happened in the past.

We use am/are/is + -ing form for actions that are not finished. They are happening in the present-future.

past simple tense timeline - completed action in the past

I worked yesterday.
She didn’t play last week.
Did you go to the restaurant last night?

present progressive / present continuous tense timeline - not finished, started, happening now

I‘m working (now). (This started in the past and finishes in the future. It is happening now.)
She isn’t playing (now).
Are you going to the restaurant (now)?

present progressive / present continuous tense timeline - future action

I‘m working tomorrow. (This starts and finishes in the future.It is happening in the future.)
She isn’t playing next week.
Are you going to the restaurant tonight?

Exercises

past or be -ing

Grammar explanations