What are the best (the "Hardest") 3rd languages to learn after knowing two languages.

I know the idea with "easy" or "hardest" languages is very subjective. But I'm sure most people can agree in the general that Japanese is generally harder than Native English speakers learning Spanish and German is probably harder than Italian. <br><br>I'm looking to transform myself into a polyglot and I have 2 languages already. I know: <br><br>1. English (Native speaker) <br>2. French (My father was born and raised there and we used to visit family there all the time). <br><br>I've learned a few more languages but I have only completed Duolingo in the following two: <br><br>1. Spanish <br>2. German<br><br>I am currently actively learning: <br><br>1. Italian <br>2. Russian <br>3. Portuguese (Portugal)<br>4. Japanese <br><br>I plan to learn around 15/20 languages in my lifetime. <br><br>This way I can work in Canada, France and be able to travel to many countries without the need of translation: Brazil and Portugal, Spain and South America, Italy, Germany, Russia and parts of Eastern Europe like Poland, Czech Republic and Slovakia. <br><br>So here's the question: knowing that I already know French and English, what would be 3 languages that are really hard for me to learn. Can you rank them in the order of hardest to least hardest?