Need help C&P is tomorrow.

I am filing for an increase to my 10 percent degenerative disc disease of the A VA doctor diagnosed me with osteoarthritis in both hips and 2 parts of the spine. But when I filed my claim they still want a C&P with an outside provider. Limited range of motion was already documented by the VA doctor. So my question is will they count the hips as secondary to the degenerative disc disease of the lumbar spine in this exam? Or is that a different claim all together? I have a feeling they’re going to try and give me the run around on this. It is all very confusing. Anything I should mention to this provider about the VA appointment with the arthritis doctor connecting this issue to my service connection. Also for context my combined rating right now is 60 percent. But only 10 percent for this and I think it should be more because I have a-lot of problems with mobility and unable to exercise (only very low impact) or go up steps very well. It had also caused me to gain weight since I can’t do strenuous exercise per a Va doctor. Please help! They gave me a C&P exam a week after a filed which seems very quick.