Files don’t open in the app I want

When you double–click a doc in Finder, it opens it in the app that macOS associates with its file type, such as .jpg or .rtf. These associations may change when you install apps. If you Ctrl-click a file and pick Get Info (select it and hit Cmd-I), you’ll see its associated app in “Open with”. You can change it for this file, or click Change All… to pick an app for all files of this kind. Or Ctrl-click a doc and choose Open With…, or drag it from the Finder onto an app.