Re: "Yes. What time will I cum?" (sic)
Looks like one of them Freudian slips. Gotta be careful not to say the quiet part out loud.
Joking aside, I recommend, "what time should I visit?" "Should" clarifies that he's flexible about the schedule and asking so he can best meet her needs, while "will" asks for her prediction, like, "when will it rain?" suggesting, "the weather service predicts you'll arrive at 3." Though "arrive" is more accurate (he's not asking when he should depart, he's asking when he should appear at her door), it's less casual. Though they're talking business, they don't look formal. It's your call.
TLDR: Please come back translator. Even if it's funny, don't jizz on your readers. Please clean that up so we can continue to enjoy your work.