Hello, sorry for my english
I need to resize my actually sd 32gb to another smaller.
I tired to resize in livelinux with gparted the ext4 partition but gives me an error.
Which error?
Is the data on the partition smaller than the size you are trying to shrink to?
Thanks for your support, in gparted i had select too small resize, i change it into a bigger and now run.
For the backup it’s very interest but its to hard, for me, without a step by step guide 
If you’ve managed to do it with gparted, all good 