I'm from Germany and I write my class, method, variable names all in english and I think most of the people do this as well. But in comments it depends on whom I'm working with.

And I have to admit if I see code written in some other language than english I really hate it cause you can't "read the code". It's like if someone would write a sentence in german mixed with english.

A other reason you definitely should use english when coding is that API calls and language specific calls are always written in english. So why switching languages? I would even say using english helps you thinking cause you don't have to switch languages.

Also all those documentations and most questions and answers on the internet are in english so IMO you HAVE TO work in english anyway.

One example I think it is horrible to see is

meinObst = "Apfel;Himbeere;Traube" meinGeteiltesObst = meinObst.split(";") for obst in meinGeteiltesObst: ...

You absolutely can see it in the for statement you are switching from one language to an other and that's not a good thing IMO.