Learn Russian: Этот целеустремлённый человек всегда вдохновлял своих друзей. - This purposeful person has always inspired his friends.

It is a compound word made of цель (goal or target) and устремлённый (directed or aimed). Put together, it literally means goal-directed, which translates perfectly to purposeful or driven.

Why is the imperfective verb вдохновлял used instead of the perfective вдохновил?

The presence of the word всегда (always) indicates a continuous, ongoing, or habitual state in the past. In Russian, such repeated or constant actions require the imperfective aspect, even if English uses the present perfect has always inspired. Grasping this continuous past aspect is crucial when you start combining these main clauses with time boundaries like с тех пор, как (since).

Why do we use своих instead of его for his?

Because the possessor (the purposeful person) is the subject of the sentence. Whenever the subject owns the object in Russian, you must use the reflexive possessive pronoun свой (here in the accusative plural, своих). If you used его here, it would mean he inspired some other guy's friends!

What case is друзей, and why does it look exactly like the genitive case?

It is in the accusative case because the friends are the direct object being inspired. However, for plural animate nouns (living things like people and animals), the accusative case takes the exact same form as the genitive case, resulting in друзей.