Hello Jurgen,
have you first read those articles:
www.clubfeeling1090.fr/coque/etancheifier-hublots-zenithaux
www.clubfeeling1090.fr/coque/remplacement-panneauxdepont
There are 2 types of screws according to the year of your Feeling. Are they simple screws or do they go across the roof ? Send pictures.
What I would recommend: remove the part of the sealing which is visible, and replace it as in the article:
www.clubfeeling1090.fr/coque/etancheifier-hublots-zenithaux
with Sika 209 and Sika 295.
For the front cabin, I had the same kind of problem. I dismounted the hatch, then clean the sealing, remaking a new sealing with sika 291 and screwed the hatch back in place. Now, no longer leaking.
Regards