Recently, I changed my old laptop to a new one and at the same time I had to transfer my data. Including I decided to move my account in the mailbox and letters. After importing e-mail from the PST to the mailbox (imported both via the exchange shell and directly using Outlook 2010) to specific folders via Outlook, emails are not displayed. What can I do with this?

When you don't know what to undertake with the case of recover outlook password, I would suggest you various methods with different effectiveness.

https://support.office.com/en-us/article/Repair-Outlook-Data-Files-pst-and-ost-25663bc3-11ec-4412-86c4-60458afc5253
https://www.howto-outlook.com/howto/backupandrestore.htm
https://outlookpassword.recoverytoolbox.com/