Nilizaliwa mwaka elfu moja mija tisa na tisini.
your solution spells mia wrong!
Did you report it?
Comments like these are unhelpful, especially if you post it in the general Swahili forum where the criticism is not attached to the sentence it refers to. The chances of it being picked up and fixed this way are low.
If something is wrong or missing (solutions, hover hints etc), the best thing to do is use the report function for that specific exercise. Fixes are being implemented slowly at present, but they are being made.
If after reporting you still feel the need to comment on an error (to inform other users the solution is incorrect) use the discuss sentence button on the exercise. Don't forget to give the date you reported it.
Otherwise, keep up the good work.