Basic game knowledge that new players need to understand:
1. There are three types of heroes: Physical, Gunpowder, and Magic. Each player can learn 9 heroes at Level 2, from any type, without conflict. However, only two heroes can be equipped simultaneously. If a player feels that a certain hero is no longer needed, they can choose to forget it. But once forgotten, all the skills trained for that hero will be lost. If you want to use this hero again in the future, you'll have to retrain it.
2. Every skill of a hero, once learned, will provide additional attribute bonuses, such as adding a few points of defense by learning a certain skill, etc. If there's time, you can try to learn all available heroes and upgrade their skills a few levels... every bit of extra attributes helps, hehe.