ISPConfig + Wordpress Theme needs simplexml and mcrypt

hello,
i run a server with ispconfig (3.2.12p1 on debian 12) and i works well.
i install a wordpress template that needs simplexml and mcrypt to work correctly. tested with a tool inside the theme.
So i try to install it on my server, but this error is shown:
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php -m | grep simplexml
PHP Warning: PHP Startup: Unable to load dynamic library './ext/simplexml.so' (tried: ./ext/simplexml.so (./ext/simplexml.so: cannot open shared object file: No such file or directory), /usr/lib/php/20220829/./ext/simplexml.so.so (/usr/lib/php/20220829/./ext/simplexml.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
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so how can i solve this problem?
thx
the icebear