Extremly long loading task, Website slow

Hey guys,

my website is extremely slow and takes around 10sec to load, but my scores on GTmetrix are really good. I am using WP Rocket Premium, optimized all images with Smush, using Google Fonts from local.

GTmetrix shows me that this task needs extremly long to load and making my website slow:
Can anyone tell me for what this is and if or how I can speed it up:
wp-json/pum/v1/analytics/?event=open&pid=2434&_cache=1588773182053

Here the screenshot from GTmetrix:
https://snipboard.io/kit4uC.jpg

Thanks for your help

The page I need help with: [log in to see the link]