All my colleagues would agree and did the same. I don't. I want äöü quickly available for chatting and other "quick" writing, while coding typing is usually not the bottleneck.

Is there a German keyboard layout such as?:

AltGr + a -> ä

AltGr + o -> ö

AltGr + u -> ü

I'm Polish and I'm very glad that our most common layout is like that for ąćęłńóśźż (with AltGr + x for ź). Currently I'm in Germany and I wonder if there is similar layout for German umlauts.

There seems to be a layout called "US international" which might help: https://en.m.wikipedia.org/wiki/File:KB_US-International.svg

As a Swede, I can echo this. I'm so used to the US layout by now that I have to do a double take whenever I switch to the SE layout, or type on someone else's keyboard.

I used to get laptops and keyboards with the US layout on them, but stopped since the resale value in Sweden drops sharply because of it. Thankfully, I've touch typed since forever so I rarely look at the keyboard anyway. (Unless, of course, I have to type with the Swedish layout.)