In my opinion, German should be the easiest language for a native English speaker to learn.
It depends. The biggest problem people have with German are the cases. we got "only" 4 of them (there are other languages which have 16... I think finnish is one of them).
In English there is no such thing. That is why English is considered by other Western countries as a more or less easy language.
Cases depend on the sentence itself and the position of the word in the sentence.
In the end, most people will understand what you are after anyway even so you dont get the right case. (It is not like that we would always be right with this neighter
As in French or Spanish we use different female and male articles (that means we dont have one word like "the" but we use three different once for male, female and words which describe an "it"). That is the reason why sometimes you will read something like "The apple who is..." and not "The apple which is...". An apple ("Der Apfel") is a "male-word" in German. The Sun ("die Sonne") is a "female-word". The car ("das Auto") is the "it"-word.
A thing that is a bit different to other languages is, that German is "case-sensitive" if you write it. All nouns are written in Uppercase (better to say the first letter of it is written in uppercase -> "Apfel"). In English and many other languages this is only the case if you write a name. "Susi eats an apple" = "Susi ist einen Apfel."
So I would say that German is slightly (not very much) more difficult to learn than Spanish. (I cant speak French so I cant say much about it, but it is considered to be as difficult as Spanish so I assume that for now.)
In Europe it is the most spoken language (mothertongue-wise). That is because it is spoken in Germany, Austria and Switzerland as mothertongue-language.
You will find the language itself on the whole planet, but here is a map of where it is spoken in Europe.
In Europe it is mainly important because Germany is one of or the most important economic country here.
German is although known in the USA, because the German pilgrins in the USA are based in Philadelphia and as that, you can find most of the german-speaking people in the area around Philadelphia.
"Is German more important than Spanish of French"? I would say no. It is important because of the economic power of Germany, but more people talk spanish or french all over the planet than German.
However Spanish is spoken in many areas which are not that powerful in a economic way. (Some countries in South-America, Spain, etc.)
However French is often spoken in although economical powerful countries like Japan because it is considered as a very "beautiful" language.
Someone told you to learn Chinese. It is true that it will become more and more important but it is although true that it is totally different from languages in the western world because of different letters, a whole other pronounciation and the fact that there is not "one" Chinese-language.
The one which is spoken by most people is "Mandarin".
But it can happen to you that you are in a part of China, where they just dont speak it.
For example in Germany there are different dialects but everybody will understand what you are saying if you speak German to them. In China there are really different languages which are spoken, not only different dialects.
I would recommend to learn one of the other western languages (like German, Spanish or French) and not to try to learn a eastern lanuage like Chinese. This is just to difficult and you will very fast hit a point where you lost all your motivation.
On the other hand: IF you can speak an eastern an a western language, you are more unique.
It is your choice.
Many more informations can be found on wikipedia.
*Fuchur*LINK TO IMAGE