Je ne peux plus faire des mises à jour

[Salim]

Apologies for responding in English.

Welcome.

What instructions did you follow to install signal ?
Can you provide a link we can check ?

If you have only been using Linux for one day, the quickest solution is probably to begin again with a fresh installation.

I was using the steps available on this link: 

https://signal.org/download/#

Code:

# NOTE: These instructions only work for 64-bit Debian-based
# Linux distributions such as Ubuntu, Mint etc.
# 1. Install our official public software signing key:
wget -O- https://updates.signal.org/desktop/apt/keys.asc | gpg --dearmor > signal-desktop-keyring.gpg
cat signal-desktop-keyring.gpg | sudo tee /usr/share/keyrings/signal-desktop-keyring.gpg > /dev/null
# 2. Add our repository to your list of repositories:
echo 'deb [arch=amd64 signed-by=/usr/share/keyrings/signal-desktop-keyring.gpg] https://updates.signal.org/desktop/apt xenial main' |\
  sudo tee /etc/apt/sources.list.d/signal-xenial.list
# 3. Update your package database and install Signal:
sudo apt update && sudo apt install signal-desktop