Step :
1. Download : https://repo.protonvpn.com/debian/dists/stable/main/binary-all/protonvpn-stable-release_1.0.3_all.deb
2. sudo apt-get install ~/Downloads/protonvpn-stable-release_1.0.1-1_all.deb
3. sudo apt-get update
4. sudo apt-get install protonvpn
5. Open Via Menu