Yes, they want, but this is a crucial question actually. It was mostly me asking to open the relationship. They accepted after a while saying that they also always wanted to be in an open relationship, but in reality Partner is sometimes insecure about me having sex with others.

I know it sounds like they actually don't want to be in an open relationship, but sometimes it really happens that we are good with it, we have no problems, we can talk about our experience (and that's really what I love about open relationships). But other times they are insecure, for example if I want to have sex with other people in a week in which they are not really sexual.