In order to become a polyglot is it better to start with hard languages or the easy ones?
Here are the languages I wanna know within some years, However, I don't know which order should I follow.
I found that studying a difficult language for a while facilitates my learning of relatively easier languages once I got back to them.
For example, when I studied Polish for an hour or two per day and I went back to my French studies that same day, I found the latter quite easier and more effortless. This continued for several months and I can say that studying a more difficult language first or concurrently (irrespective of which type of language group it is from) boosts my language learning capacity greatly.
If your aim is to become a polyglot eventually, I would recommend that you learn a main language from whichever types of languages you prefer. I see you have two Romance languages and three Germanic lanugages. Why not add a Slavic language to that list? The reason for this is that languages from the same groups (or others) often contain cognates, which are basically words 'shared' between certain language types (or others), that you might recognise and guess the meaning to.
That being said, I would suggest starting with the language that you find most difficult from the list you have there (it might be French or Italian), or perhaps even trying out a Slavic language for a while and see if that knowledge does the same for you as it does for me.
I recommend starting with an easy one. It should make the next one less difficult. So, I would learn them in an ascending order, from easiest to hardest.
As for which will be easiest or harder for you, a general ranking will be based on your native language. Some languages lend themselves to be easier depending on the language(s) you already know.
As an English native speaker, I found This chart helpful. It might have another chart for people from a different native language. I'm not sure though.
However, that is only a general assessment. Some individuals find what is easiest and hardest for them, is different from others who share their native language.
I would take the Norwegian and Swedish one at a time if I were you and I can safely say that for almost everyone, Italian is easier than French, also German presents more of a difficulty than Norwegian and Swedish due to it having some fairly complex grammar in comparison. As far as easy languages go, you've already started the easiest of all, Esperanto. In reality, everyone's brains work differently and everyone finds different languages more enjoyable. If you try all the languages you are interested in your heart will tell you which path to follow.