State of Survival How to reset and up the level of your heroes to ameliorate matchmakings RR

My first real tuto
How to reset all your heroes and reup them to level 80
and why ?
Better for matchmakings Reservor Raid it seems
Eveyone do that , so don’t hesitate if you meet always big alliances…
I hope it will help all to have better fights during reservor raid