why did he struggle in the re-lighting the fire? and what was the man's opinion of the old-timer's advice now?

The man re-builds the fire because he made the mistake of lighting the first fire under snow covered branches. The fire melts the snow and it falls, putting out the fire. In a last ditch effort to start the fire he tries again. The man obviously regrets that he didn't take the old man's advice to stop and make camp earlier. The man regrets that he did not respect nature's warnings.