Learn Hardcore Russian: Мы любим общаться с друзьями после работы. - We like to socialize with friends after work.

Russian often uses любить + infinitive to express liking activities: Мы любим общаться... = We like to socialize. You can also say Нам нравится общаться с друзьями, which is equally correct; it’s a bit more neutral/impersonal in tone (literally “it pleases us to socialize”). Remember: нравится needs a dative pronoun: мне/нам нравится.

What does the -ся in общаться do, and can I drop it?

The -ся makes the verb reflexive/reciprocal. Общаться means “to communicate/socialize (with others).” You can’t drop it here; there is no everyday verb общать with this meaning. The perfective partner is пообщаться (“to have a chat/socialize for a while”).

What case is с друзьями, and why that ending?

It’s instrumental plural. The preposition с meaning “with” takes the instrumental: с кем? с друзьями. Note the irregular noun друг → друзья (nom. pl.), and instrumental plural is друзьями. Examples: с другом (with a friend, sg.), с друзьями (with friends, pl.).

Why is it после работы and not после работа?