GitHub - getkirby/staticache: Static site performance on demand

Have uploaded the dir to plugins

Have insert code in config.

Have insert data in htaccess - funny, where should be:
Add the following lines to your Kirby htaccess file, directly after the RewriteBase rule.

I have more than one RewriteBase rule there. I add it after:

RewriteRule ^kirby/(.*) index.php [L]

RewriteCond %{DOCUMENT_ROOT}/static/%{REQUEST_URI}/index.html -f [NC]
RewriteRule ^(.*) %{DOCUMENT_ROOT}/static/%{REQUEST_URI}/index.html [L]

Now i get:

 Whoops \ Exception \ ErrorException (E_COMPILE_ERROR)
Declaration of Kirby\Cache\StatiCache::retrieve(string $key) must be compatible with Kirby\Cache\FileCache::retrieve(string $key): ?Kirby\Cache\Value