Supporting someone with a stutter?

Supporting someone with a stutter? So, I myself don’t stutter, but I recently started dating someone who does. We have great chemistry together and things are going quite well, but at times I can tell his speech insecurity bothers him. I want to support him or help in some way without being unintentionally condescending or causing more stress. I can’t imagine how stressful having a stutter already is, and I would just like to offer support however I can. I haven’t met anyone else with a stutter before, so I would genuinely love to hear what others who stutter have found to be helpful from the people around them. And also perhaps what behaviors they have found to be UNhelpful- even from people with good intentions.