Why i can't start learning with two vitality?
Solution 1:
It looks like you have already increased your health once using two vitality. This will have got you a "Skill: A stronger physique" card. As the message says you will need to study this (along with four vitality) to increase your health again.
A similar principle applies when improving reason and passion (except with different skills).
I should note that I can't actually see the card on your play area - if you can't find it check behind other cards to see if its hidden there.