My first idea were some like so: "Es ist eine große Ehre mit Ihnen in Kontakt zu treten." Is it ok? What would you say?
P.s. he is much more older as me.
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As I wrote in my comments, this question is partly OT and difficult to answer, as the exact circumstances are not known. Think about that politeness is different in German - English people switched to the polite form "you" at some point and dropped thou, and then you of course became profane. We still have three distinctions (Sie, Sie with given name and Du), and this reflects into the rest of the language. How polite someone is to me - has to be - depends on a variety of factors:
So my boss can be less polite if he tells me to do something, especially if he has to remind me because I'm overdue; but he has to be more polite if he wants something I'm not obliged to do, like some private favor. I think that is different in English, as Germans working in the US/GB told me that polite remarks to your work can actually mean "that's the worst crap I've ever seen".
To be too polite is not a good idea; as we have those distinctions, we have to use it. It would be awkward if my boss asks me: "Is it possible to look after ?". I might come to the conclusion that he's playing some strange game with me. On the other hand, he cannot say "Sie haben mir bis morgen die Zahlen vorzulegen" if he just assigns me a task and has to expect that I will do it. I would then think that he doesn't have trust in me to do my work properly, or he just think that I am a low servant.
Now let's think about a VIP making a contact request to me: yes, he is higher ranking, but not in respect to me. That someone is the CEO of a multinational corporation is not relevant if I don't work for him or want to be his supplier/work with him.
So I assume he is either interested in you or your company. I would then stay polite, thank for his interest, but keep my distance. If I'd think that he's rather interested to my company than myself, I would use "we" in my answer.
And in the end he'll probably see that you're not a native speaker, people tend to be somewhat forgiving on that.
I would probably resort to:
"Sehr geehrter Herr (Dr.) X,
ich bedanke mich für Ihr Interesse und verbleibe mit freundlichem Gruß [optional: nach town]