sudo graylog-collector-sidecar -service install
graylog-collector-sidecar: commande introuvable on cento7 
how can i fix it
there you downloaded the files, but did no install. You need to use rpm or yum (both with parameter; Google will help) to install the package. After the installation you can use the command
“commande introucable” == “command not found”, i guess?
I guess you are not willing to read what other wrote to you.
What does this posting tell you?
yum install won´t work. You shall not search for any mirrors. You already downloaded the rpm. Try localinstall instead…
And please translate the error-messages for us. I didn´t speak/read france for a few years
No package collector-sidecar-0.1.8-1.86-64.rpm available
thats why you should try localinstall instead of install. The mirrors won´t know the package 
excuse me I did not understand well localinstall centos7
If you don´t understand something, just say it 
It has nothing to do with centos, but with yum.
localinstall is a parameter for yum. You can take a look on all parameters with:
man yum
If you still don´t know how to use it, try to google.
Thanks for your help @Lyro 
now I can collect firewall logs through Graylog 2.5 , it is my first time with graylog 