>pls give me some tips and tricks
Equip mAtk items on magical attackers, and pAtk items on physical attackers. Don't forget about survivability — gear matters.
Build a proper party with a tank, support units, and damage dealers.
>any chance to resets levels
No, you can't reset levels.
>The priest and Paladin form how its work?
If you're asking about the MC's class: you can switch between them and have a different unit in combat.
If you're asking about Talent Trees: those affect all your units.