Very long loading time

Hi all,
using any wp version, I get a VERY slow loading time.
This is not because of the webserver (other pages open well), neither the database server (phpBB/others open fine).

I deleted all the layout, putted in on other page, and included the “layoutless” wp, but it gives the same speed…
The link to the root of blog is: https://blog.janmarques.net/
Any idea how to solve?

Thanks ??