Pagespeed problems

Hello dear balbooa team,
in the last months we found that on many of our sites the pagespeed ranking is very low. Now we created a new site, which does not have GA or any other thirdparty script that could be the cause.
The pagespeed initially was at 60%. Then we activated gridbox performance plugin, almost every setting (HTML, JS, CSS minification, defered loading, lazy load images & caching) - and strangely it went down to 42% after. Although FCP got better, but the other ratings went up.
Could you please have a look at the site if we're missing anything - we will send you login data through the form.
It would be great to know if there is a general solution or fix, since this happens to many of our sites.
Thanks a lot in advance!

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