Many internet, phone and other companies employ young people for support tasks who can speak english most of the time, so it shouldn't be a big issue. Especially if you go to offline stores in Berlin to fill out the forms.
Don’t bother trying it before you actually move though, because the website appears to be geo-locked and the American and UK versions aren’t open yet.
> an online-only bank
It's a direct bank as any other, quick internet search will reveal more options in Germany. Their "innovations" in comparison with personal banking even in neighbouring Czechia (e.g. Fio), or Poland (e.g. mBank, Inteligo) are laughable.
I had originally tried getting an account in a Sparkasse branch, but it was much more difficult than N26. No doubt there are other online only banks, but I cannot comment on their quality without using them.
Can vouch for Berlin, too. In Berlin Mitte near Alexanderplatz there are great apartments for approx. $2k/month (around 60m2). It's one of the more expensive areas, but I think it's better for young families who want a calm place.
You will make way less money, though. $5-7k/month should be possible. At SAP you can make $10k/month after some years. But in general it isn't really comparable to US salaries.
For the lang. barrier: Most people speak english and there are many coffee shops where 80% of the employees can only speak english.
Alternatively: I heard that Zurich also pays good, but that the people are not too social and it can be hard to build a social circle there.