Learn Hardcore Russian: Друг увлекается фотографией и делает красивые снимки. - A friend is into photography and takes beautiful shots.

увлекаться is a reflexive verb meaning “to be keen on” or “to have a hobby.” The suffix -ся makes the verb reflexive, showing that the subject is doing something to or for themselves—in this case, indulging in an activity they enjoy.

Why is фотографией in the instrumental case?

Because увлекаться always asks the question увлекаться чем? (“to be keen on what?”) and takes the instrumental case. Here фотографией is the instrumental form of фотография.

Why is there no possessive pronoun before друг? Doesn’t it mean “my friend”?

Without мой, друг means “a friend” in a general sense. If context implies “my friend,” Russians often drop мой. If you want to emphasize possession, you would say мой друг.

In делает красивые снимки, why are красивые and снимки in their nominative forms?

The verb делать takes a direct object in the accusative case. Since снимки (photos) is inanimate, its nominative plural form снимки is identical to its accusative plural. The adjective красивые agrees with that form (nominative/accusative plural).