Recently I was asked to translate "I forgot all my Russian" - this came from a native English speaker, which, in English, makes sense.

"my Russian" here is referring to her ability to speak Russian.

I quickly responded "Я забыла все по-русски" but then realize there is no "my"

Also, shouldn't it be "Я забыла как говорить по-русски" or could you say "Я забыла все русский язык"

Which would be the best translation, if any?