why "This house is the smallest" is wrong?
You forgot the translate the second "ev." Your sentence is simply "Bu ev en küçük."
I know but until now had no idea that the translation should be literal. don't think that my translation has any different meaning
I support this - unless you can phrase "is the smallest" in Turkish without repeating the noun ("ev") as well as you can do in English.
Would it be possible to say 'Bu en küçük ev.'?
Yes, and that would be: This is the smallest house.
I typed 'Bu ev en küçük el' and it was marked correct. This is a mistake, right? El is not somehow also correct?