Are these A level choices good to study physics in Russe group unis?

You probably should strongly consider A-level FM for places like Imperial and Oxbridge.
Taking 4 A-levels confers no advantage and it's not really recommended to do 4 unless two are maths and FM.

In truth I wanted to physics, maths, fm and German but for maths I got a grade 7 and the minimum entry requirement was a grade 8 in my school so I stuck to geography

In truth I wanted to physics, maths, fm and German but for maths I got a grade 7 and the minimum entry requirement was a grade 8 in my school so I stuck to geography

*further maths

I would suggest dropping the fourth subject in any event. Perhaps ask your school if you can start doing the AS FM or something in the interim?
Otherwise you may be somewhat less competitive for those specific unis, although most other physics courses including good physics departments at other unsi (in the RG or not) should not be that concerned by it.
You could also explore taking FM in a gap year if you are unsuccessful in applying.

In my school I was told if I do well enough for AS maths exams like 85%+ average in year 12 I can do AS fmaths in year 13

I specifically want to study physics at Russel group unis such as imperial and kings college London etc
And Oxbridge.
The alevels I chose are:
Maths
Physics
Geography
German

Not 100% sure about other russel group unis but ik oxbridge require at least three out of maths, further maths, physics or chemistry. You don't by any means need all four - three great relevant a levels are better than four okay ones, and tbh you want to enjoy your last two years at school as much as you can. If I were you I'd keep whichever out of geography and German is most important/enjoyable to you, and swap the other for either further maths or chemistry. From my own experience, I do physics, maths, further and German and I honestly love the combo, but only you know what's best for you at the end of the day, so try to figure out what you'd get the most out of. Just make sure you look on some of these unis' websites so you know which subjects you need to study physics. Also just remember most schools and colleges have a couple weeks at the start of year 12 (I'm guessing you're year 10/11) where you can still change your subjects, so don't stress too much, you've got loads of time. Sorry if this reply's a lil too long, but I hope it helps. Good luck with everything!!