It seems like you're saying, once you've gone through 90% of the effort to learn a language, you've only got 10% left (as opposed to 10% for basics then 90% to master).
Yes, that's right, except for the important part. I'm sure the percentages are off, but here's the basic idea:
To correctly form simple German sentences you need to learn 90% of the non-vocabulary elements of the language. To get to mastery, you have to learn the other 10%.
To correctly form simple English sentences you need to learn 10% of the non-vocabulary elements of the language. To get to mastery, you have to learn the other 90%.
