Your are getting errors when trying to connect to the database using the built-in SQL database credentials.
During installation, SQL Server Database Engine is set to Windows Authentication mode.
Change Authentication to mixed mode.
To change security authentication mode:
In SQL Server Management Studio Object Explorer, right-click the server, and then click Properties.
On the Security page, under Server authentication, select the new server authentication mode, and then click OK.
In the SQL Server Management Studio dialog box, click OK to acknowledge the requirement to restart SQL Server.