Learn Russian: Он всегда поздно уходит из офиса.

The word всегда (always) shows that this is a repeated, regular habit. For habitual actions, you need the imperfective verb уходить. If we were talking about him leaving the office just once in the future, we would use the perfective уйдёт.

Does уходит mean he literally walks away on foot?

Уходить is formed from ходить (to go on foot), so its core meaning is to leave by walking. However, when talking about leaving work, school, or an event, Russians commonly use уходить to mean 'to depart' in a general sense. He might drive or take a bus once he's outside, but he is physically walking out of the building.

Why does this sentence use из офиса instead of от офиса or с офиса?

To say you are leaving a place, the preposition depends on what preposition you use to say you are at that place. Since you work inside an office (в офисе), you must use the opposite of в, which is из (out of). If you were leaving 'work' (на работе), you would use the opposite of на, which is с (с работы). Both из and с require the Genitive case ending, which is why we see офиса.

Why are the adverbs всегда and поздно placed before the verb?