Sorry ! I always forget logs…
I Try on another Hetzner VPS for test with fresh install too and it’s same results.
Thank for your help 
The reason why i want to switch on testing is because i want to make a fresh install of my production server which are switched accidentally on Testing and I cannot restore Yunohost Core Backup from this server on a stable version.
curl https://install.yunohost.org/switchtoTesting | bash
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 462 100 462 0 0 1335 0 --:--:-- --:--:-- --:--:-- 1339
----
Patching sources.list to enable testing repository...
----
----
Running 'apt-get update'
----
Hit:1 http://mirror.hetzner.com/debian/packages bullseye InRelease
Get:2 http://mirror.hetzner.com/debian/packages bullseye-updates InRelease [44.1 kB]
Hit:3 http://deb.debian.org/debian bullseye InRelease
Get:4 http://deb.debian.org/debian bullseye-updates InRelease [44.1 kB]
Get:5 http://security.debian.org/debian-security bullseye-security InRelease [48.4 kB]
Get:6 http://mirror.hetzner.com/debian/security bullseye-security InRelease [48.4 kB]
Hit:7 http://forge.yunohost.org/debian bullseye InRelease
Hit:8 https://packages.sury.org/php bullseye InRelease
Fetched 185 kB in 2s (76.3 kB/s)
Reading package lists... Done
----
Running 'apt-get dist-upgrade'
----
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
