The more Stars you have on your card, the stronger the card is from the beginning. Since the Star quantity is decided when you receive the card, it is not possible to increase the Star quantity for that specific card.

However, once you keep upgrading a certain card, it is possible that a 2-Star card with higher levels to be stronger than a 3-Star with lower levels, and so on!

Thus, please keep upgrading your cards to have a stronger battle deck!

Thank you for your support! 😊