Could you please correct my mistakes.

You've described a warm friend who's cooling off.

You've- subject
described- verb
a- adjective
warm- adjective
friend- direct object
who's- who: direct object/ is: verb
cooling- verb
off- preposition

Corrected:

You - subject
've described- verb
a- adjective
warm- adjective
friend- direct object
who's- who: direct object/ is: verb
cooling- participle (verbal adjective) modifying "who"
off- preposition used in a "phrasal verb" situation: http://grammar.ccc.commnet.edu/grammar/verbs.htm#phrasal

=)

You've is a contraction of You and have.

looking for simple subects. we spentmost of the day picking berries in the woods.

Looking for simple subjects. We spent most of the day picking berries in the woods.

Simple subjects are the main noun or pronoun in a sentence that performs the action or shows a state of being. In this sentence, the simple subject is "we." "We" is the pronoun that represents the person or group of people who spent the day picking berries.

The verb in this sentence is "spent." "Spent" shows the action of how the subject "we" used their time.

The prepositional phrase "in the woods" modifies the verb "spent" by describing where the action of picking berries took place.

So, to summarize:
- Simple subject: we
- Verb: spent
- Prepositional phrase: in the woods
- Action: picking berries