Physics, Computing and Maths are the ones to keep. The extended project is good also (especially since you're doing stuff closely linked to electronics) but you may find that the 'non standard-ness' of it as a course may stop it from being useful
Physics and maths go together nicely. Computing is a good way to show you're already interested in the subject (and goes a long way to proving you have some kind of competence that can be expanded) - however, it does depend on exam board. Some of the Computing syllabuses are closer to generic ICT.
WJEC Computing is a surefire winner though (programming + two projects + analysis) and that helped me into uni
EDIT: Also, keep in mind that whilst German shows some additional skills / that you're "well rounded", they will take that into account even if you drop it after AS.
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