He doesn't stop entirely, but he does slow the pace a little, give her more time to adjust to the sensations. His fingers don't try to press any further in yet, instead just rubbing against the inner folds, letting her adjust to the sensations there with periodic attention to her clit, attention that becomes a bit more frequent when she seems to be getting used it.

"Is it like you expected?" he asks, plenty cheeky because he's quite sure Gustavain had little idea of what to expect, but he is clearly taking great pleasure in the introduction.