C# retrieve data from Bored API

Question

I'm trying to retrieve data from https://www.boredapi.com/api/activity, a public API, with the following code in C#:

namespace TesteAval
{
    public partial class Form1 : Form
    {
        private List<Activity> ActList;
        private Activity Act;

        public Form1()
        {
            InitializeComponent();

            LoadActivities();
        }

        private async void LoadActivities() 
        {
            var client = new HttpClient();

            client.BaseAddress = new Uri("https://www.boredapi.com/");

            var response = await client.GetAsync("/api/activity");
            //var response = await client.GetAsync("/api/activity?key=5881028");

            var result = await response.Content.ReadAsStringAsync();

            if (!response.IsSuccessStatusCode)
            {
                MessageBox.Show(response.ReasonPhrase);
                return;
            }

            ActList = JsonConvert.DeserializeObject<List<Activity>>(result);
            Act = JsonConvert.DeserializeObject<Activity>(result);

            listBoxDashBoard.DataSource = ActList;
            listBoxDashBoard.DisplayMember = "TypeActivitySimple";
        }
    }
}

Already made the conversion via postman (retrieved the json) and converted to C" (via json2c#). My goal is to create a List ActList with 10 objects but get an error. Also tried to retrieve just one object to var Act but got another error. I tested this exact same code (with different class from json2c#) with another API http://cambios.somee.com/api/Rates and it works.

Also already have the class (from json2C# converter):

namespace TesteAval
{
    public class Activity
    {
        public string activity { get; set; }
        public string type { get; set; }
        public int participants { get; set; }
        public double price { get; set; }
        public string link { get; set; }
        public string key { get; set; }
        public double accessibility { get; set; }

        public string TypeActivitySimple
        {
            get
            {
                return $"{activity} - {type} ";
            }
        }

        public string TypeActivity 
        {
            get 
            {
                return $"{activity} - {type} - {participants} - {price} - {link} - {key} - {accessibility}";
            }
        }
    }

}