Let's Simplify it 

 HttpClient client = new HttpClient();
                string url = $"{baseURL}/Repositories/{repositoryName}/Token";
                Dictionary<string, string> data = new Dictionary<string, string>();
                data.Add("grant_type", "password");
                data.Add("username", "admin");
                data.Add("password", "admin");
                HttpResponseMessage response = client.PostAsync(url, new    FormUrlEncodedContent(data)).Result;
                string content = response.Content.ReadAsStringAsync().Result;               
                dynamic serializeResponse = JsonConvert.DeserializeObject(content);                          
                string token = serializeResponse["access_token"];

this will get you the token string without RestSharp