Heading to Cartagena at the end of March. Any recommendations/advice

My friend always wanted to see Colombia and we planned a trip to Cartagena. We'll be there for about 10 days. About 3 days will be spent at a resort and the rest will be in an Airbnb in the old city. I have been to Medellín several times but never to Cartagena. Although my trips to Medellín were with my ex who is half Colombian and half Brazilian and fluent in Spanish. I know a bit of Spanish which has helped me in the past but far from fluent.my friend speaks none. What do you guys recommend as far as trips and activities. We're just going for travel. Not looking to necessarily meet women.