Which language to use as base, when learning a new language

[LinguaPony]

I use both Russian and English as base languages to learn both Italian and Mandarin Chinese. Depending on the circumstances.

[Willow]

As for me the best way to learn foreign language is to learn in a comparison with native one, or, to be more specific, use my native language in order to build another language basis (and further) in my head.
It doesn't works so well while using my second foreign languages in process of learning, though, sometimes I'm compelled to use English or Polish in order to complete some courses in German. But, nevertheless, I've noticed that in this case I almost subconsciously translate these materials in Russian in order to understand information completely

[William Camden]

English generally, though I have used German materials to learn Turkish and once learned some Kurdish (in Cyrillic script) via an elderly Russian-Kurdish dictionary published in Soviet times.