Ok, after almost a day with everything working just fine and Xpenology online, internet was just gone again, so i tried this, internet worked for a few minutes, and then it was gone again.
What i did was first let Xpenology choose the IP, then reserve it on the router.
Without restarting the router, i unplugged the cables, plugged them again and internet was there for all my devices, except Xpenelogy.
So i restarted Xpenology, but it was not reachable, best i got was "connection error" on Synology assistant.
So i restarted the router, and et voila, Xpenology was online again.
For some reason i understand the router blocks Xpenology.
I´m starting to lose hope, it worked for almost a day, then it doesn´t work...and i can´t find a reason for this at all.