Wokay, not sure to understand how you ended up loosing the signature keys for both repos … But let’s try this:
wget -O- https://forge.yunohost.org/yunohost.asc -q | apt-key add -qq - >/dev/null 2>&1
wget -O- https://archive.raspberrypi.org/debian/raspberrypi.gpg.key -q | apt-key add -qq - >/dev/null 2>&1