Salvatore. Please ask your shared hosting provider for details.
Ideally your provider enables the required extensions in the master php.ini. In some cases, a local php.ini might be recognized if php runs as a cgi binary (as opposed to an apache module); in this case, the php.ini file has to be copied into every working directory that php code is executed from. (Rather than figure this out, some will recommend simply copying it into every subdirectory.)
If you know the extensions exist but aren’t being loaded, you could try modifying piwik to load these modules dynamically at runtime. See the example in http://php.net/dl