A lot or a little?
Parents need to know that Overloot is an arcade game for iOS and Android devices. It has no objectionable content. While players do kill monsters and other people with swords and similarly sharp objects, there's no blood or gore, because the visuals in the game are rather cartoony. It also has a focus on progress by ads or paid transactions. When you die, you can keep going by spending in-game currency or by watching ads. Said currency can also be earned by playing, or bought with real money.
Read the developer's privacy policy for details on how your (or your kids') information is collected, used, and shared, and any choices you may have in the matter, and note that privacy policies and terms of service frequently change.