We had a great time in Croatia and when you have enough time we recommend going to Split or Budva. You can also go to Kotor but we found it to be a bit too small and preferred Budva. To Split you can either take a ferry or a bus and to Budva you can take a bus as well.
You can book the ferry to Lopud here: getbyferry.com/en/dubrovnik-lopud
You can book the 3 island tour here:
www.getyourguide.com/elaphiti-islands-l2283/elaphiti-islands-full-day-tour-from-dubrovnik-t21953/?partner_id=QO4B9J0&placement=content-middle
Free Walking Tour: www.guruwalk.com/de/walks/36882-von-der-altstadt-zur-landung-des-konigsref=aafqyxxq08p8t2dfyniq
Some of these links are affiliate links
Timestamps:
00:00 Intro
00:17 boat tour
03:55 city center
05:21 mount Srd