1. Check what directories are in your $PATH 
    echo $PATH
/opt/BurpSuiteCommunity/:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/bin
 
2. Add directory to PATH temporarly 
export PATH="/opt/BurpSuiteCommunity/bin:$PATH"
 
3.  Add directory to PATH permanently   
vim ~/.bashrc
export PATH="/opt/BurpSuiteCommunity:$PATH"
4. Execute command:
cd /opt/BurpSuiteCommunity/
sudo ln -s /opt/BurpSuiteCommunity/BurpSuiteCommunity burp
5. Run command:
burp