Isn't that different politeness levels? Can you use 나 with 습니다 politess level?
Actually you can. The politness ending is for raising the listener and using the humble pronoun is for lowering youself. You can choose to raise the listener without needing to lower yourself.
The problem is, I dont think an app like Duo should use sentences like that because a lot of people using it doesn't know these things, these details, and it itself does not provide any info about it. It should not use sentences like this.
Actually, they put that info on their "tips" but it's not available on their mobile app yet. You can access it on the desktop version.
Not native but i think this would be weird
I agree. I know its a thing you technically can so, but I have never heard it in media or in my 4 months I lived in Seoul.
If you live in Korea and watch baseball you should probably hear it almost every day.
Fix this already please , everytime i make a mistake its not my fault but yours
i use 나는 혼자 요리해요 why is it not correct ?
It's correct. As the course is in beta please report it.
And still not corrected 7/14/18 - reported again.
When would you use 혼자서? :)
"나는 혼자서 요리합니다." is also accepted. The meaning is the same but the grammar there is quite complicated; you may just consider 혼자서 as an emphasised form.
I was thinking "by myself" means without assistance, not alone
What is 혼자? Is it formal or casual and how do you use it?
It means 'alone' or 'by oneself'. It can be used in any levels of formality and politeness.
what @AlexHaimov said -- we should not be mixing 나 and ~합니다. different politeness levels!
at the least, simply 혼자 요리합니다 should be accepted as well. please fix.
It is very natural to mix 나 and -ㅂ니다. Also please submit full sentences when no context is given.
isnt myself 자신
It is, but not in the sense of "by myself", meaning "alone".
What is wrong with 저는 혼자 요라헙나다?
Should be "요리", but you wrote "요라". And should be "합니다", but you wrote "헙나다".