How may language requirements be formulated under requirements or preferred qualifications?
It is fine to specify language requirements in terms of “good knowledge”, “very good knowledge”, etc. in a language that is necessary in order to perform the work in question. Do not forget to write in the announcement that the language(s) will be required in the performance of duties/day-to-day work, as it may otherwise raise issues of discrimination. Example of a standard formulation: The ability to express yourself well in English, as this will be required in day-to-day work.