Can I browse the Billetto events in another country? (Mobile app)

Yes, you can. When you register on Billetto, visible events are initially of the country in which you've registered your Billetto account.

To view the events in another country, tap on the "Profile" (smiley face icon), choose "Settings" and tap on the "Country" section. Pick the country you'd like to view the events for (currently you can choose Denmark, Norway, Sweden, UK, The Netherlands and Germany) and tap "Change" on the top-right. Now you can browse the events in the country of your choice.