MAMP and creating new user and MySQL

I’m using MAMP on a new user on my Mac, but I have some problem with MySQL files.
I’m able to see all the db files from PhpMyAdmin, but when I go to localhost I see the Welcome page of WordPress with the famous 5 minutes install. I choose the name of the site (even though the site already exists and has contents), but for the username it says it already exists, and when I put my email address and I click install WordPress I have this huge block of errors like:

`Errore sul database di WordPress: [Can't create table 'fdl_users' (errno: 13)]
CREATE TABLE fdl_users ( ID bigint(20) unsigned NOT NULL auto_increment, user_login varchar(60) NOT NULL default '', user_pass varchar(64) NOT NULL default '', user_nicename varchar(50) NOT NULL default '', user_email varchar(100) NOT NULL default '', user_url varchar(100) NOT NULL default '', user_registered datetime NOT NULL default '0000-00-00 00:00:00', user_activation_key varchar(60) NOT NULL default '', user_status int(11) NOT NULL default '0', display_name varchar(250) NOT NULL default '', PRIMARY KEY (ID), KEY user_login_key (user_login), KEY user_nicename (user_nicename) ) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci

Errore sul database di WordPress: [Can't create table 'fdl_usermeta' (errno: 13)]
CREATE TABLE fdl_usermeta ( umeta_id bigint(20) unsigned NOT NULL auto_increment, user_id bigint(20) unsigned NOT NULL default '0', meta_key varchar(255) default NULL, meta_value longtext, PRIMARY KEY (umeta_id), KEY user_id (user_id), KEY meta_key (meta_key(191)) ) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci`

and it continues on like this. Can anybody please help me fix this issue? Thanks.