I am afraid i have irrevocably ruined my 6 year old son's will to think by giving him overly challenging thinking tasks. is that effect even possible?

Not likely: Without knowing more information cannot say it the tasks would even be considered over challenging for his age. Perhaps it was more the manner in which they were presented and not the task. Children of that age should be encouraged to be curious and learning should be fun. Physical activity is key and taking a walk outside as way to stimulate learning is much better than playing computer games.