Si arriva con una bella passeggiata non ti occorre molto tempo il museo era già chiuso quando siamo arriivati

see the website indeed

Bom dia Fabrício, não tenho está informação pois sou mais um viajante que conheceu este local maravilhoso no verão.

Yes, it is open, 7 days a week, from 10:00 am through 5:00 pm. The hours will be shorter after September first. There is an admission fee, with discounts for children students and seniors. It also offers a family ticket.

We actually were there in April and the tourist office told us it would be open but it was not. When we arrived the sign on the door posted hours and days but nevertheless it was closed all day. This was the only time we encountered this in all of Norway. Other museums were very organized. So the moral of the story is: when you get there, just go and hopefully you will be able to get in. If it is the same week as Easter, it will be closed the entire week.

アーケシュフース城とその要塞にはないと思います。 宿泊するもしくは宿泊したホテルに一時預かりしてもらったほうが良いでしょう。

The Akershus Castle at the fortress is open Monday - Saturday 10:00 - 16:00, and Sundays 12:00 - 16:00. Enjoy! :)

You can, but I think it is paid entry.