WordPress specialist needed: Time To First Byte >1.5 sec.

Problem Our Swiss website (see screenshot attached) is created with WordPress and is a copy of our Germany-Site with the same domain and ending with .de (further referred to DE-Site; Swiss Website referred to as CH-Site). The CH site is hosted with a Swiss company. The server is quick, a file (uploaded here: [login to view URL]) loads in <100ms. The DE-Site has a TTFB <50ms. Anyhow, the CH-site has a TTFB of >1.5 sec. The site itself is fairly optimized for speed. Basics like GZip compression, combining CSS files etc. are done. Also Ranking on e.i. GTMetrix is good and not behind our DE site. Your Job Please identify the problem why the TTFB is so high and fix the problem. The approach We can grant access to WP. In a screensharing Session we can also grant Root-Access. Anyhow, we will only do such screensharing session after having reviewed your detailed approach in writing, how you plan to identify and solve the problem. How to apply With your application please give us with a first idea how you plan to identify and solve the problem. Even if you give us the solution for the problem we will still award the project to you. The better and more detailed your approach is, the more likely you will be assigned the job. Please note that we will not assign the job to anyone sending a generic application. Budget: We pay a fix EUR 50,00 for successful completion of the task.