We use the simple present tense:
1. For habitual actions or actions which are repeated in the present.
I usually wake up at 8 o'clock.
2. For permanent states in the present.
I am a teacher and I teach Geography. I go to school by bus.
3. For general truth:
The Moon goes round the Earth.
We use infinitive verb without to with I, you, we, they. We ad 's' at the end of the verb in third person singular.
I like my students.
My teacher likes me.
We use 'don't' before verb to make a negative sentence.
I don't give much homework.
We use 'doesn't' in third person singular. (he, she, it)
He doesn't like Geography.
We use 'do' or 'does' to make an interrogative sentence.
Do you like your school?
Does he like Geography?
Yes I do. Yes, he does. Or, No, I don't. No, He doesn't.