Are all language trees equal in length?
Is so, what is the shortest, and the longest?
Not really, the shortest tree from English is High Valyrian, while the longest is German or Norwegian.
Well, Norwegian has 117 skills.
German and Dutch are 1 skill away from each other, with German in the lead (I'm pretty sure german has 124, I can't remember the exact number, but I know dutch is 1 less, and they both have more than Norwegian)
BUT, German has 3 bonus skills... so If you don't count those, Dutch has more skills.
EDIT: now that I think about it, I'm not sure whether or not I was counting the bonus skills, so I'll get back to y'all on that
Courses also vary in length depending on the starting language.
For instance, Russian -> German course has only about 70 skills.
Also, courses differ within the same pair. E.g., Russian -> English is 55 skills long while English -> Russian is 79, so they are not like simply reversed versions of each other.
The German for English tree has 121 skills if you are not counting the 3 bonus skills.
But one course can have more skills than another one, but more lessons in total, right?
Language courses are all different in size, and made specifically for the source and target languages that they teach from and to.
I do not know though the answer to the second part of your question.
No. Not nearly. Some trees (Czech, German, and Norwegian included) teach over 2,000 words, while some (Japanese and High Valyrian included) teach 1,000+. I believe the shortest is High Valyrian, and the longest is either German or Norwegian.
I was wondering the same but in terms of lessons not skills (though I know it is pretty hard to find out)
Just some examples (bonus skills in parenthesis): German from English 121(3) skills, German from French 117 skills, French from English 78(3) skills, French from German 68 skills, Dutch from English 123 skills, Norwegian from English 117 skills, Italian from English 66 skills.