I have installed Arch Linux ISO on USB. And In BIOS I did not disable security boot, because I thought it is not good idea. I have started to find decisions to my problem, and most popular answer was disable security boot. If I disable my security boot, it will be safe for my PC? Maybe do you have any other decisions? And why my PC require it for Arch Linux but for Debian not?


Personally, I find Arch Wiki a fantastic resource for answering majority of my questions regarding Arch setup and operations. Usually information is well condensed there, and links and references are provided for further research. Specifically for the secure boot, one can read here 
https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot . I hope you can find it useful too. Please note that Arch Wiki articles are translated in many languages!

If that doesn't work, my next step is to search Arch forums. This page covers Secure Boot:

If that doesn’t help either, then stack exchange comes to the rescue: 

After all these resources, I very rarely (never) have any questions remaining for the community.