What's wrong?

You don't say
I am not understand
wrong
you say
I don't understand
or
I didn't understand

am/were/is/was mean adalah

I am a teacher
Saya adalah seorang guru

You cannot say

I am teach English
wrong
you say
I teach English

I thought you were asleep

I thought you were asleep.
I fikir awak tidur.

thought= past tense of think (verb)
were = verb to be for past tense
asleep = adjectve (kata sifat)

I like swimming

Gerund = VERB + ING

Gerund can be a subject (perkara)

Swimming is my hobby.

Gerund can be an object (objek)

I like swimming

A Road To Heaven

Remember singular (one) and plural (more than one).

One road.
Two roads.
One way.
Two ways.
One of the ways to combat inflation is to spend less.

Its Colour

Its : possessive pronoun
I like its colour

All the common contractions with subject it are really grammar markings:

it's [meaning 'it is'] Progressive or Passive
[meaning 'it has'] Perfect
it'd [meaning 'it would'] Conditional
[meaning 'it had'] Pluperfect
it'll [meaning 'it will'] Future

It's nice to see you.