Within Sitefinity can I collection data from a API and then join that data together with data that is Sitefinity database. I been thinking about this because there are control and tools in Sitefinity that it would be nice to leverage and can use the review mode.
You can use the Sitefinity API to create the Content Items in your Sitefinity site, e.g. News. Then, you can use the Sitefinity UI to add images or other media to the already created news item.
This should get you started: https://www.progress.com/documentation/sitefinity-cms/for-developers-create-a-news-item-with-the-native-api