Minecraft version: 1.16.3
litematica version: Litematica v.0.0.0-dev.20200913.215807
mod version:

when i use the easy place mode the rotation of the piston and observer are not correct

PS: i am french and i don't speak very much english

If you are in single player, then previously you would have needed Tweakeroo also installed to handle the rotation requests. This was also implemented in Litematica directly in the 2021-09-17 build for 1.16.5, and in the 2021-09-06 build for 1.17.1.

If you are on a server, then the server would need a mod to handle the rotation request. Currently the two mods that do that are the CarpetExtra extension mod to FabricCarpet, and the separate/alternative QuickCarpet mod. The accurateBlockPlacement rule also needs to be enabled (with /carpet setDefault accurateBlockPlacement true).