I am not sure what you meant to write.  I have tried below to give a possible different way of phrasing this.

The first exercise

I learned how to tell time in English.  The word "it" is difficult.  I don't understand how "it" is used in a sentence.

Русскоговорящему всё понятно))

Something like that:

The begining/First of all.

I'm learning English tenses. It's hard. I can't understand how is it possible to understand them.

{the first

I learn times for english.. the it is difficult..i dont't understand as it is possible to understand?}

First of all!
I'm learning English tenses. It's hard. I can't understand how is it possible to understand them