need help on ddos protection

Hello i need help
i run vpn on Softethervpn
and i set ip tables to block everything but some attack not effect the server its only bypass to the vpn server and i use ovh game server is there any advice to block all traffic its bypass my vpn server

second
i wan ddos protection to stop botnet or L7 on my ovh game i host my site on it but its with L7 down
is there any advice ?

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