I suggest that you first code for flexibility for at least the first few iterations of your site. Think of it as a fail fast optimization. Because you will be learning a lot and finding better ways to do things, you want to keep it as cheap as possible for as long as possible to explore different alternatives to your initial website concept(s).
Other than that, don't focus on languages too much. Find a way for you and your partner to write 'services' with language agnostic interfaces. If done correctly, there's no reason why you couldn't have parts of your site built in every one of the languages you mentioned. Naturally, the extra flexibility this affords you comes at a cost of being much harder to do correctly.
Other than that, don't focus on languages too much. Find a way for you and your partner to write 'services' with language agnostic interfaces. If done correctly, there's no reason why you couldn't have parts of your site built in every one of the languages you mentioned. Naturally, the extra flexibility this affords you comes at a cost of being much harder to do correctly.