How we cite our quotes: (Part.Chapter.Paragraph), with the exception of Part V, which runs (Part#. "Short Title". Paragraph). Part V has no numbered chapters—only title headings.
Quote #4
Marketa let herself be made love to by this mechanical male body, then watched that body flinging itself between Eva's legs, but she tried not to see the face, so as to think of it as a stranger's body. It was a masked ball. (II.12.5)
Sex and love are problematic in Kundera's work, mostly because of identity issues and problems with communication. Marketa doesn't know how to access her own sensual pleasure until she finds a way to "decapitate" her husband in her mind. When she doesn't have to deal with his face (i.e., his proper identity), she doesn't have to think about their history together. And without the pain of the past, sex finally becomes pleasurable.
Quote #5
But Tamina did not push him away, and her grimace and averted head aroused him enormously. None of the few women he had known up to now had ever responded so eloquently to his caresses. (IV.20.14)
Hugo doesn't strike us as the most appealing human being. He's got smelly breath, and to be honest, he's a total predator. He promises to fetch Tamina's notebooks for her from Prague, but it's in order to get close to her and force her into a sexual relationship with him. In fact, it's actually Tamina's revulsion that arouses Hugo (since he's never been able to get a response from any other woman). This doesn't help Tamina work out her attachment issues at all. In fact, this act of sexual violence pushes her deeper into isolation and a desire to die.
Quote #6
She had once undergone minor surgery without anesthesia, forcing herself during the operation to review English irregular verbs. Now she tried to do the same by concentrating entirely on her notebooks. (IV.21.1)
Why is Tamina having sex with Hugo when she thinks of it as if it were a root canal? It's hard to say. It's possible that she's just trying to stay in his good graces so that he'll retrieve her notebooks from Prague. It's equally possible that she's simply the victim of a sexual predator who sees that she's vulnerable and has no problem exploiting that. Kundera hints that it may be a combination of these two things: Tamina feels trapped into continuing this traumatizing encounter because of her desire to keep her past life with her husband intact.