The string you have shown has strictly nothing to do with the ISO-8859-1 encoding. It's just a string containing HTML encoded entities. To decode it you could use the HttpUtility.HtmlDecode
function:
string myString = "Betrakta nedanstående figur";
string myDecodedString = HttpUtility.HtmlDecode(myString);
Note that you will need to reference the System.Web
assembly in order to use that method.