Hi,

I want to use a VPN connection from my windows pc through my suse firewall to another pc in the internet. Is there the need to install freeswan on my firewall

No, you dont`t need but perhaps it is better to do so your hole lan can use this vpn connection freeswan is ipsec... do the vpn server in the internet use ipsec???

or can I just open the needed ports ? (which ports must be opened ?)

which vpn do you want to use?? ipsec??? pptp/chap??? there are so many vpn versions with so many difficult ports!! mfg tobi sorry my englisch isn`t so good