não consigo usar apt-get no debian 9 [RESOLVIDO]

uso debian 9 32bits
quanto tento instalar qualquer programa aparece a mensagem, exemplo:

root@localhost:/home/x# apt-get install lxde

Lendo listas de pacotes... Pronto

Construindo árvore de dependências       

Lendo informação de estado... Pronto

E: Impossível encontrar o pacote lxde 

sendo que ja ajeitei a sources.list
cujo conteúdo é:

# 



# ddeb http://deb.debian.org/debian stretch main

deb-src http://deb.debian.org/debian stretch main



deb http://security.debian.org/debian-security stretch/updates main

deb-src http://security.debian.org/debian-security stretch/updates main



# stretch-updates, previously known as 'volatile'

# A network mirror was not selected during install.  The following entries

# are provided as examples, but you should amend them as appropriate

# for your mirror of choice.

#

# deb http://deb.debian.org/debian/ stretch-updates main

# deb-src http://deb.debian.org/debian/ stretch-updates main

deb http://http.debian.net/debian jessie-backports main 

tem alguma coisa errada? o que será?
não consigo instalar audio no debian 9, nem driver de rede.
driver de ethernet é RTL8723BS module
e áudio nem sei. pois o comando

alsamixer 

nem funciona.

Remova o # e o d duplicado:
Errado: # ddeb http://deb.debian.org/debian stretch main
Correto: deb http://deb.debian.org/debian stretch main

Remova o #:
Errado: # deb http://deb.debian.org/debian/ stretch-updates main
Correto: deb http://deb.debian.org/debian/ stretch-updates main

Salve as alterações (Ctrl + X) e rode o comando apt-get update

/etc/apt/sources.list

## Main

deb  http://deb.debian.org/debian stretch main contrib non-free

deb-src  http://deb.debian.org/debian stretch main contrib non-free



## Updates

deb  http://deb.debian.org/debian stretch-updates main contrib non-free

deb-src  http://deb.debian.org/debian stretch-updates main contrib non-free



## Security

deb http://security.debian.org/ stretch/updates main 

deb-src http://security.debian.org/ stretch/updates main



## Backports

deb http://http.debian.net/debian jessie-backports main

deb-src http://deb.debian.org/debian/ stretch-updates main 

# apt update && apt upgrade

Jovem, jovem, jovem.... sua sources.list está toda torta!

resolveu