Cannot install MySQL in Ubuntu 18.04

Question

I am new to MySQL and I am having trouble installing it for a few days now. I was running MySQL and these are the things that I did.

mysql -u root -p

and entered my root password, then I created a new user using

mysql>GRANT ALL PRIVILEGES ON *.* TO 'ananyapam'@'localhost' IDENTIFIED BY 'password';
mysql>\q

Entered using the new user

mysql -u ananyapam -p

(Succesful!) Then tried deleting the new user ananyapam using

DELETE FROM mysql.user WHERE user = 'ananyapam';

Now when I listed my users and there was no user ananyapam. However, now when I try to create the user ananyapam again using

mysql>GRANT ALL PRIVILEGES ON *.* TO 'ananyapam'@'localhost' IDENTIFIED BY 'password';

it returns an error message. Not understanding much after a while of searching, I thought of removing and then reinstalling it using the commands below:

 sudo apt-get purge mysql-server mysql-client mysql-common mysql-server-core-* mysql-client-core-*
 sudo rm -rf /etc/mysql /var/lib/mysql
 sudo apt-get autoremove
 sudo apt-get autoclean

I then tried to reinstall MySQL using this

 sudo apt install mysql-server
 sudo mysql_secure_installation

it returns error

ERROR 1045 (28000): Access denied for user 'debian-sys-maint'@'localhost' (using password: YES)

This link might be useful for someone:Access denied for user 'debian-sys-maint' - installing mysql?

Edit: @Melebius suggested the other answer but after

mysql> SELECT user,authentication_string,plugin,host FROM mysql.user;
+------------------+-------------------------------------------+-----------------------+-----------+
| user             | authentication_string                     | plugin                | host      |
+------------------+-------------------------------------------+-----------------------+-----------+
| root             |                                           | auth_socket           | localhost |
| mysql.session    | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost |
| mysql.sys        | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost |
| debian-sys-maint | *477880DFF7642ABC170F60991A43E7FFB8B000E4 | mysql_native_password | localhost |
+------------------+-------------------------------------------+-----------------------+-----------+
4 rows in set (0.00 sec)

it returns an error message

mysql> CREATE USER 'debian-sys-maint'@'localhost' IDENTIFIED BY 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for 'debian-sys-maint'@'localhost'

Any help is appreciated.