How many of the same phonemes in the German language are found in the English language? Same consonants? Vowels? Resources for this?
The only context where "same phoneme" makes sense is if identity is based on a fixed and universal feature system like the SPE system, and underlying forms are fully specified (because underspecification leads to a immense degree of indeterminacy what the feature values are in a single language). You also have to make some analytic assumptions about what is phonemic in either language (such as whether there is a flap phoneme in English).
"Phoneme" or "phonemic" has at least two meanings, so you would have to specify what meaning of "phoneme" you have in mind. One meaning is "present in underlying representations". The other is "is not fully predictable as a variant of some phoneme, looking only at surface phonetic segments" (so, is not strictly allophonic, as would be the case with the rounded and non-rounded variants of /ɹ/). The intermediate territory between these two concepts includes the flap (which can come from /t/ or /d/) or aspiration (caused by stress differences which are then neutralized, as in capitalistic versus militaristic).
There are a number of other analytic choices that need to be made, for example, in "gate", is there a vowel [e] that is distinct from the vowel of "get"? One answer is "yes, it's [get] vs. [gɛt], and another answer is "no, it's [gɛɪt] vs. [gɛt]. Since [ɛɪ] is, in the SPE system, a sequence of phonemes and not one phoneme, the analytic question is whether to add a new segment /e/ (as opposed to a new sequencing of existing phonemes). For German, one can analogously treat [ø:] and [œ] as long and short variants of the otherwise same vowel [ø(:)].
Then you also have to decide what dialect of the language you're interested in, since some dialects of English lack [θ ð] and others lack [ɔ]. My rule of thumb is that if someone doesn't specify dialect, I get to use mine. In the case of German, I'm not a native speaker, but I will use the values of the dialect that I tried to learn in high school.
Oh, and you also have to decide how to deal with marginal phonemes like English [x] as in "Bach" or German [θ]. I think one should be really conservative in admitting such phonemes, because if you're not, English would end up having phonemic /q/ and /ʕ/ as exemplified by words like [ʕira:q] "Iraq". And what about the click in the language name Xhosa? You'd need to set some kind of social criterion for filtering out recherché pronunciations by people in the know, if you feel that [ʕira:q] is too unacceptable but [bax] is acceptable.
In other words, it seems like a straightforward question, but it totally isn't.