Learn Spanish (Latin America): Te lo doy para que desempaques el impermeable rápidamente. - I am giving it to you so you unpack the raincoat quickly.

Because it follows the phrase para que (so that). While the adverbs of probability you are learning right now (like tal vez or quizás) can take either the indicative or the subjunctive depending on how certain you are, para que ALWAYS triggers the subjunctive because it expresses an unrealized purpose or goal.

Why is there a spelling change to qu in desempaques?

The infinitive is desempacar. To keep the hard k sound of the original verb when it is followed by an e in the subjunctive, the c changes to qu. If it were spelled with a c, it would sound like an s.

In Te lo doy, why are there two pronouns before the verb?

Te means to you (indirect object) and lo means it (direct object). When a sentence has both, the indirect object always comes first. Because doy is a conjugated verb, both pronouns must go directly in front of it.

Why does the word rápidamente keep its accent mark?

When you create an adverb by adding -mente to an adjective, you use the feminine form of that adjective (rápida). If the original adjective has a written accent mark, like rápido, the adverb keeps it in the exact same place.