Hello, I do not intend to answer the question you have not asked, but I would be very careful about invitations for writing a paper. They may come from predatory publishers. MDPI has got a controversial reputation when it comes to that; see, e.g., https://www.lib.cas.cz/podpora/data/asep/predatori/predatory_journals_eng.pdf (from slide 11 on). Best wishes!