Right click a file of the type that you want to change or reset its default application setting. Example right click a .pdf file to change or reset the default application that will be used when opening .pdf files.

Next: choose "Open With"

Next Select "Choose another App"

Next Choose the App you want to use and if setting the default make sure to check the option  "Always use this app to open"

That's it clicking files of that type will now always open in the app you selected.