Alberto is very helpful in guiding about what to visit in Oslo! His apartment is right at the centre of the city, also very clean, stylish and full of basic amenities! Both Nationaltheatret and Oslo central station are walkable!
Everything else to visit in the city is within walkable reach. It depends on personal choice to explore the city by walk or by bus! My preference is to walk.
Alberto is very flexible for the check-in times as well. I would definitely recommend this place and would love to visit again.
Best,
Shivdev