English has Present, Past, and Future tenses of verbs. However, each tense contains up to four forms. It is very important to know which of the forms to use and what this usage means in speech or in writing.
An English verb usually has two characteristics:
Engleski jezik ima sadašnje, prošlo i buduće glagolsko vreme. Međutim svako vreme ima do četiri oblika. Veoma je važno znati koja se forma koristi i njeno značenje u govoru i pisanju. Engleski glagol ima dve najvažnije karakteristike.
1) vreme - Present, Past, or the Future tense;
2) aspect - it is Indefinite, Perfect, or Continuous.

The Present Indefinite Tense
Sadašnje neodređeno vreme opisuje uopštenu radnju ili stalnu aktivnost koja nema određena vremenska ograničenja.

Example - Primeri:

He wears glasses. - On nosi naočare.
What do you study at school? - Šta učiš u školi?
Sometimes we meet and go to the movies.
Ponekad se sretnemo i idemo u bioskop.

The Present Continuous Tense Sadašnje trajno vreme opisuje aktivnost koja se dešava u sadašnjem trenutku.

Example:

To write: He is writing a letter now.
Pisati: On piše pismo sada.
To wait: I am waiting for a bus.
Čekati: Ja čekam autobus.
To read: We are reading the book together.
Čitati: Mi čitamo knjigu zajedno .
To play: Children are playing baseball in the park.
Igrati se: Deca igraju bezbol u parku.

The Present Indefinite vs. Present Continuous

Example:

Student: What do you do?
Teacher: I'm a teacher.     Present Indefinite

Student: What are you doing?
Teacher: I'm teaching.    Present Continous

General questions

A general question requires the answer yes or no. In English such a question is formed by placing an auxiliary or modal verb (exceptions see below) at the beginning of a sentence: Have you ever been to London? Was he reading when you came? Can you help me? Shouldn't I do it?.
A polite answer to a general question typically includes the auxiliary verb that was used to form the question:

Have you been to London ? - Yes, I have.

Was he reading when you came ? - No, he wasn't.
Does he know you ? - Yes, he does.
Did I mention it ? - No, you didn't.

A negative question requires 'no' to be confirmed, and 'yes' to be denied:

Don't you see it? - No, I don't.

(not allowed: Yes, I don't)

Don't you see it ? - Yes, I do

(not allowed: No, I do).

Specific questions

The answer to a specific question is a concrete piece of information. A specific question always contains a question word, which is placed in the first position before an auxiliary verb. The subject comes after an auxiliary verb but before the main verb.

Example:

What is your name ? - My name is Alex.
Where do you live ? - I live in London.

Question words are interrogative pronouns and adverbs: what; where; when; why; which; who; whose; how; how many; how much (for uncountable objects); how long, etc.

Example:

When do you usually come home ?
What is he doing ?
How can I help you ?
Why did they behave like this ?
How many bottles of wine are you going to buy for the party ?
How will we find a road to the town ?

Exceptions:

The full-meaning verbs to do and to have, as well as modal to have to and need require the auxiliary to do:

What do you do professionally?
What do you have there?
How much time do I need?
Why did he have to do it?

If any of the question words who, what, which refers to the subject of the main sentence, the auxiliary verb to do in the question is omitted. The main verb, in this case, has the same form as in the initial sentence.

Example:

The little boy goes to school... Who goes to school ?
This news made me happy...What made me happy?

The third shelf contains science fiction books... Which shelf contains science fiction books ?

Be careful to avoid mistakes like: Who does go to school ?