on terminal or ssh write the following command 

Step 1: Uninstall the Firefox Snap:

sudo snap remove firefox

Step 2: Create an APT keyring (if one doesn’t already exist):

sudo install -d -m 0755 /etc/apt/keyrings

Step 3: Import the Mozilla APT repo signing key (if wget is missing, install it first):

wget -q https://packages.mozilla.org/apt/repo-signing-key.gpg -O- | sudo tee /etc/apt/keyrings/packages.mozilla.org.asc > /dev/null

Step 4: Add the Mozilla signing key to your sources.list:

echo "deb [signed-by=/etc/apt/keyrings/packages.mozilla.org.asc] https://packages.mozilla.org/apt mozilla main" | sudo tee -a /etc/apt/sources.list.d/mozilla.list > /dev/null

Step 5: Set the Firefox package priority to ensure Mozilla’s DEB is always preferred. If you don’t do this the Ubuntu transition package will be reinstalled, and you’ll have the Firefox snap:

echo '
Package: *
Pin: origin packages.mozilla.org
Pin-Priority: 1000

Package: firefox*
Pin: release o=Ubuntu
Pin-Priority: -1' | sudo tee /etc/apt/preferences.d/mozilla

Step 6: Finally, use APT to remove Ubuntu’s pretend Firefox DEB (if still present) and installed the real-deal from Mozilla’s repository:

sudo apt update && sudo apt remove firefox
sudo apt autoremove -y

sudo apt install firefox