Try this LLM suggested way.
// Create individual TimeSpan objects
TimeSpan time1 = TimeSpan.FromHours(25);
TimeSpan time2 = TimeSpan.FromHours(25).Add(TimeSpan.FromMinutes(30));
// Add the TimeSpan objects together
TimeSpan totalTime = time1.Add(time2);
// Output the total time as string
string result = totalTime.ToString(@"%h\:mm");