Present continuous (I am doing) или simple present (I do)?

Study this explanation and compare the examples:

Present continuous (I am doing)
Use the present continuous to talk about something that is happening at or close to the time of speaking:

I am doing

Simple present (I do)
Use the simple present to talk about things in general or things that happen repeatedly:

← I do →

past now future past now future

The water is boiling. Could you turn it off, please?

Listen to those people. What language are they speaking?

"Where's Tom?" "He's playing tennis."
(you find a stranger in your room) What are you doing here?

Maria is in Canada for three months. She's learning English.

Use the present continuous for a temporary situation:
I'm living with some friends until I can find an apartment.

Mary usually has a summer job, but she isn't working this summer.

Water boils at 100 degrees Celsius.

Excuse me, do you speak English?

Tom plays tennis every Saturday.
What do you usually do on the weekend? What do you do? ( = What's your job?)

Most people learn to swim when they are children.

Use the simple present for a permanent situation:
My parents live in Boston. They have been there for 20 years.
Jack doesn't work during the summer. He always takes a long vacation.

Some verbs are used only in simple tenses. For example, you cannot say "I am knowing."
You can only say I know. Here is a list of verbs that are not normally used in continuous tenses (but there are exceptions):

want	 like	 belong	 know		 suppose	 remember
need love see realize mean forget
prefer hate hear believe understand seem
(meaning "possess") think (meaning "believe"/"have an opinion")

  • Do you like Rome? (not are you liking)

  • He doesn't understand the problem, (not he isn't understanding)

  • These shoes belong to me. (not are belonging)

  • What do you think Tom will do? ( = What do you believe he will do?)

  • Do you have a car? (not are you having)

  • but:
  • What are you thinking about? ( = What is going on in your mind?)