conditionals - Are "If I could" clauses always followed by "would"?

I always see

If I could ... I would.

For example,

If I could speak English, I would go to English-speaking countries.

Is there a rule against a conditional clause which contains could, being followed by another could in the main clause?

For example,

If I could speak German, I could understand this essay.

I am a native American speaker but I do not know if the above is actually wrong.