Hi there (Name??)
although it is a German forum I'll answer it in English. Remember: best way to learn the language is to speak it
oil:
Since I live in the States I've no clue how good of a supply of Kendall oil you can expect in Germany. I would go with Castrol (a BP brand). Some test have show that the flash point is one of the highest. Presumably you don't drive your car in 'real' winter condition I would go with a 10W-40.
fuel:
MOZ vs. ROZ - European octane numbers are different than US/Canadian. Without bothering with the formula the lowest ROZ (Europe) = highest MOZ (US). 'Normal Benzin' is absolute fine for your 356.
I would not recommend any 'lead additive'. A can of Marvel oil every second filling is just fine for mine.
So, mehr englisch ist nicht
Mach' dir keine sorgen wegen rechtschreibfehlern, grammatik oder anderes - ich bin mir sicher, alle foren teilnehmer vergeben dir ...
In diesem sinne
Cheerio
William