Tenses

to express an interrupted past activity.
While we were playing tennis, it started to rain.

to express an incomplete activity in the past in order to contrast with the
past simple that expresses a completed activity.
I was reading a book during the flight. (I didn’t finish it.)
I watched a film during the flight. (the whole film)

to make clear that one action in the past happened before another action in
the past.

When I got home, I found that someone had broken into my apartment
and had stolen my laptop, so I called the police.

to stress the activity or the duration (in a similar way as in the present perfect
continuous)

We had been playing tennis for about half an hour when it started to
rain heavily.

for decisions made at the
moment of speaking
(spontaneous)
OK, I’ll come for a run with you.

for future plans, decisions and
intentions made before the
moment of speaking
We are going to paint this room
blue.

for future facts
I will be away for two weeks.

for predictions based more on
an opinion than a fact
I think that the inflation will fall to
three percent next year.

for predictions based on a
present fact / present evidence
It’s not going to rain. There isn’t a
cloud in the sky.

We use will to make offers and promises.
I’ll help you if you like.
I’ll always be here when you need me.

We use shall + I / we in questions to make offers or suggestions
Shall I carry this bag for you?
Shall we go swimming on Saturday?

We use the present continuous to talk about arrangements (= fixed plans,
usually involving other people and specific times and places)
I’m playing tennis with Sue on Monday evening at the sports centre.

Sometimes there is no difference between an arrangement (present
continuous) and an intention (going to).
I’m visiting / going to visit my sister this weekend.

We use the present simple to talk about timetables and fixed programmes.
My train leaves at 09:15.
The first lesson starts at 07:35.

is used for something we expect to be happening at a particular time in the
future. (in the middle of doing something)
This time next week, we’ll be lying on the beach!

is used for something that will happen as part of a routine.
Trevor will be cleaning the house tomorrow. He always does it on
Saturday.

is used to describe a complete event or action at a point in the future.
Call me at six thirty – I’ll have finished work by then.

is used to stress the activity going on up to a point in the future.
I’ll have been learning to play tennis for a year in May.