Thanks for ur thinkwork. now it works to have internet while pptp connected from within the lan. I clicked to add a new forward rule and added in the iptabels parameter section the following: -i ppp10. Then just clicked confirm (and save) and got the following rule:
9 * * ACCEPT all opt — in ppp10 out * 0.0.0.0/0 -> 0.0.0.0/0
now it works.
To allow acces from the wan i have added on input chain tcp port 1723 and the GRE protocol on ETH01. Tomorrow i can test if that works i hope.
Thanks for your nice and versatile router/firewall software!