i didn't understand the root form/base form of verb still?
The root/base form of the verb is the absolutely basic form. It is from here that the form of the verb can’t get any smaller. There are no endings, and nothing in front of it.
The root form of a verb can be used as either a verb or a verbal. As a verb it expresses present time and may have 'I' as its subject. For example, I drive, I have, I write. As a verbal, it is often preceded by the word 'to'. For example, I like to drive, She wants to have a party, etc.