Hai Julia,

You can try to export the website view from Odoo 8 ->10. Then import it in the V10 Db,

Thanks

1. Log in to the backend as an Administrator.
2. Make sure you have Technical Features enabled.
3. Click Settings.
4. Scroll down to Technical.
5. Click User Interface to expand.
6. Click Views.
7. On the top-right, click the down-arrow next to open the advanced Filter.
8. Click Advanced Search.
9. Under Advanced Search scroll down, and click on Whether this view is a web page template (complete).
10. Click the Apply button.
11. Select the records you want to export and choose Export from the button above

@Niyas, yes that was also my idea. I already tried the export via CSV. But I had trouble with import the CSV in Odoo 10.
Then I tried to migrate the single views via copy & paste to the new Odoo10 system.
So, I tried now this way:
1. Search for website template views   (as you wrote)
2. Copy the code under Tab architecture 
3. Make a "New Site" in Odoo 10 Edit Mode with the same name as original site. 
4. Paste the code of the Odoo 8 view in Odoo 10 view and save.
BUT this does not work for pictures... Which is because I started with a fresh Odoo 10 database. 

Would be nice to know if there is any faster way or if this is the fastest I can do it. 

No, there is no automatic process as long as you did not pay for a migration. The fastest way is to rebuild the website anew in Odoo 10.