Translation:I have received a piece of cheese for my birthday!
Liza hi! Duo doesn't accept " a small piece", because "piece of cheese" already suggests a little part/bit of it. Een "stukje" kaas in Dutch is sufficient to represent the idea of "some/a part", it's idiomatic and doesn't need "small". We aren't sure here if this "stukje kaas" is so particularly small indeed! Cheers.
"I have got a piece of cheese for my birthday!" should also be accepted, yes?
"Have gotten" is proper U.S. English, whereas "have got" is proper British English; both should be accepted, in my opinion (and yes, I have reported it).
Hi Jio, perhaps the speaker esagerate a bit, but I suppose that the sound is that "ch" as you mentioned. It's always stronger in the Netherlands, than how I would pronounce it. That is because I am Flemish, and that type of sounds are pronounced softer in "Vlaanderen". Cheers! Lu.