What I found, I should have when updating from 12.1.0 to 13.0.0-B2 I have to use the PHP version 5.6 and from version 13.0.0-B2 have to use the PHP version 7.4 ??? 

UNA requires PHP 7.4. Please note the following version requirements for older UNA releases: PHP 5.6 is required for versions before 13.0.0-B2, PHP 5.5.10 for versions before 10.0.0-B1, and PHP 5.5.0 for versions before 9.0.0-RC7. Ensure your server environment is running the appropriate PHP version.

According to this, it should be like that, in the evening I will try to see if I can move somewhere.

But unfortunately I don't know if it's a mistake because I can't upgrade... I'll just try my best.