Why I lose?

The best hand is 2 pair AA, JJ, and your opponent wins because they have the queen kicker, which beats your 8.

In that spot your opponent’s kicker was higher. You both had two pair, but their Q beats your 8, so they take the pot. Easy to miss when you’re new.

Always remember - poker hands are the best FIVE cards. Having a third pair is meaningless since a third pair require SIX cards. Your best five, as others have pointed out are AAJJ8; you opponents best five are AAJJQ

Which is better AAJJQ or AA88J (in your mind) aka AAJJ8 (computer).
The sign you not ready for this game.