Migration of ISPConfig 3 to new server

Hello
after use this tutorial....Tutorial link: https://www.zvonimir-buzanic.from.hr/migration-of-ispconfig-3-to-new-server
the websites are showing up the the default apache2 webpage rather than the wordpress content and the email client software is connecting but can't authenticate domain users/mailboxes to send/recevice messages.
* Comments... i am quite sure that the problem is that etc files from old server should be migrated to the new one...but probably just a few ones....i would not unzip the complete etc zip from old server to the new one...once to me seems that it will cause problems regarding the ip address, etc
peaces of mail.log
Jan 22 05:14:01 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 1 seconds before retry
Jan 22 05:14:01 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 1 seconds before retry
Jan 22 05:14:02 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 5 seconds before retry
Jan 22 05:14:02 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 5 seconds before retry
Jan 22 05:14:07 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 25 seconds before retry
Jan 22 05:14:07 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 25 seconds before retry
Jan 22 05:14:11 vps postfix/submission/smtpd[26867]: warning: unknown[xxx.xxx.xxx.xxx]: SASL PLAIN authentication failed: Connection lost to authentication server
Jan 22 05:14:11 vps postfix/submission/smtpd[26867]: disconnect from unknown[xxx.xxx.xxx.xxx] ehlo=2 starttls=1 auth=0/1 quit=1 commands=4/5
Jan 22 05:14:32 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 125 seconds before retry
Jan 22 05:14:32 vps dovecot: auth-worker(26872): Error: mysql(localhost): Connect failed to database (dbispconfig): Access denied for user 'ispconfig'@'localhost' (using password: YES) - waiting for 125 seconds before retry

 

Really Nice....after migrate emails&logs&www&ispconfigs and the etc/apache2/sites-enabled and sites-available with the vhosts regarding the websites in the old Ubuntu 14.04 ISPconfig to the new one 16.04...
and used the the following commands in the new server:
cd /tmp
wget -O ispconfig.tar.gz https://git.ispconfig.org/ispconfig/ispconfig3/repository/archive.tar.gz?ref=stable-3.1
tar xfz ispconfig.tar.gz
cd ispconfig3*/install/
php -q update.php
* this last line is very important, once use update command rather than the installl...and answering yes to reconfigure permissions and configurations....made all the new services work perfectly....

Command to tar the files from the old server to import to the new one:
"cd /
tar -pczf old_backup.tar.gz /var/vmail /var/log /var/www /usr/local/ispconfig/interface/lib /usr/local/ispconfig/server/lib
tar -pczf etc-old_backup.tar.gz /etc
mysqldump -u root -p --all-databases --events > /var/www/html/old_db.sql"

Relevant Comment: Prefer to have the same passwords to Mysql databases(Dbispconfig, postifix, etc) in the two servers that will make the things much more easier...to migrate
Many Thanks Till and Florian