In English, clauses introduced by "when" or "if" generally aren't used with "will" even when they clearly refer to the future. "When you will finish work" is pretty unnatural for most dialects of English.
In Swahili, you can indicate whether a "when" verb is distinctly for a future meaning with -takapo- or when it is present (and thus probably habitual) with -napo-
takapomaliza kazi, nitasafiri. = When I finish work, I will travel.
napomaliza kazi, ninazima taa ofisini. = When I finish work, I turn the lights off in the office.