In his autobiography Surprised By Joy Lewis talks about studying Latin, French, and German (as a teenager) with a tutor and the tutor's wife. He specifically notes that his German "has remained that of a schoolboy," so we can at least assume that he was less proficient in that language than in the others. How proficient he was in the others I'm not sure, since he doesn't mention much about it beyond the fact that the study method employed by the tutor and his wife was to set Lewis to translating as much of his assigned foreign-language text as he could, on his own, and then go over it with him afterwards. But those three languages at least I know he did study and learn to an extent, and he does mention that this study method worked pretty well.