Hi illi
First of all, being a foreigner is no problem whatsoever, there is many people from many cultural backrounds working for easyjet.
About your visa situation, your best bet is to email the recruitment team from easyjet to find out for sure. However, I believe you need the right to travel freely and unrestricted within the EU which of course includes the UK. If you need a visa for the UK you probably won't be able to work for any UK airline.
If you'll achieve German citizenship in two years time you certainly can apply. Until then, gain as much customer service experience as possible.
But once more, check your visa requirements and restrictions and then check with easyjet, then you will know for sure what your options are.
Good luck!