Maybe allow me to ask another question regarding this topic.
After your help, I thought I set up a new installation with encryption and lvm.
After setting up the partitions and installing the system, I went into the boot menu like before, but this time the .efi file did not show up.
It did not show any file system at all.
I only encrypted the root and the swap partitions, not the efi nor the boot partition.
What did I do wrong?