For many polyglots and hyperglots, the question "how many languages do you speak is a very complex question." Just giving a number is almost meaningless. If two people both speak 20 languages at high levels we still cannot compare their accomplishments without knowing the languages.
Likewise, discussions of language difficulty should be complex but they are often simplistic without proper perspective.
You can read/download my papers related to foreign language acquisition and culture adaptation at https://kyusan-u.academia.edu/TimDeanKeeley