Problem with updating to MacOs catalina

Hi all! I am trying to update my macbook air 2018 from macOs mojave to macOs catalina. The update downloads without any issues but than the error displays and it says that it is impossible to define the version of macOs catalina and i have to start downloading the update again. What can I do with that? I am trying to install the update for the third time and when i tryed to do it 2 times there were errors. Thank you!

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#1 alternate method

try disk maker X. you need a flash drive or external hard drive partitioned. what the app does is creat a bootable install of macOS Catalina. you can get it from diskmakerx.com. you should be able to after the bootable install of Catalina is create, open the install macOS Catalina installation file from the flash drive and it should upgrade correctly. if that does not work, boot from the drive in the startup disk preference in system preference, then run the install from their. hope this helps,
Daniel