aktivate Better WP Security and mysql gone away

I’m assuming you had it working before, deactivated it, and you’re trying again, correct?

Yes

OK. You’ve got some old settings in there. Try removing the “Better WP Security” section from .htaccess to start. Then, take a look at wp-config.php and verify all your database settings are correct.

heya
i remove the “Better WP Security” section from .htaccess
database settings ok

i remove the plugin “Better WP Security”
i install new
i activate “Better WP Security”
but the website say “mysql gone away”

and i can not deaktivate the plugin in
https://xxxxxx.org/wp-admin/plugins.php

only remove the plugin per ftp works

It sounds to me as if your MySQL server is having issues with the DBDelta function that creates/updates the database tables. You could try increasing MySQL cache to see if that fixes it or disabling all other plugins and see if that gives it enough to activate. Frankly, in the case of the latter you will have issues when the plugin updates and I would not advise it.