I might first note that it did not happen in the first place, which is unusual for my PC to do so.
Lately, I had to reinstall the Ubuntu-based Distro "Zorin OS 16" due to wrecking the EFI Partition since I wanted to dual-boot Windows 10, which meant I had to resize the EFI partition, which meant no luck before. After reinstalling, the boot time was the same again, so I had to restore my data that I made before reinstalling. I copied everything except for /etc, /usr, /boot and other directories.
Most of them had permissions for "root" user only, so after reboot, I had to recursively ch-own my user home directory. After that, the boot time took a long time.
Analyzing, it refers to the "plymouth-quit-wait.service" on what takes a long time. I searched through forums and other webpages, only to no luck. I disabled "NetworkManager-wait-online.service" and still no fast boot.
By now, I don't have any further ideas on how to make my PC boot faster. I'll leave the zip file for download, which contains the outputs from the commands "systemd-analyze".