Failed! Error: SET PASSWORD has no significance for user 'root'@'localhost' as the authentication method used doesn't store authentication data in the MySQL server. Please consider using ALTER USER instead if you want to change authentication parameters.

Open Your terminal 

sudo mysql

CREATE USER 'myuser'@'localhost' IDENTIFIED WITH caching_sha2_password BY 'mypass';

GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'localhost' WITH GRANT OPTION;

exit..

Or  try to install

sudo apt update
sudo apt upgrade
sudo apt-get install mysql-server