The “Frankfurt, Germany - Dynatrace” location has a long back log ( more than 90 tests ), so I’m wondering if there is some other issue going on there.
So… wp.com is adding 1+ second of time for each asset served off their site.
I’d say first optimization for your site is move all assets off wp.com onto your own site.
Then if your site requires additional tuning, likely you’ll require moving to different hosting, as your current hosting is using NGINX (a serious performance killer) + PHP-5.6 which reaches end of life in 18 months or so.
Suggested optimization steps
Use Apache-2.4.25 + PHP-7.1.3 + MariaDB-10.1.22 (MySQL that works) + OpenSSL-1.0.2k as your target LAMP versions.
Tune Opcache + verify enough memory available.
Tune MariaDB (mysqltuner) + verify all settings good, especially connections + temp files.
Move /tmp off disk into memory (tmpfs), for blistering fast MariaDB + PHP sessions.