Does anyone know how to solve it?

[kyky365]

done

[mutexe]

you're going to have to at least attempt to write something.
then you can ask some more specific questions.

[kyky365]

done

[mutexe]

A WeekDays object should be able to store an array of strings

so it looks like you need to replace your line 8 with

std::vector<std::string> days;

if you can use vectors, or something like

std::string days[7];

if you can't.