Ninja Storm
Veteran
I average around 45-50 for 4x4. I use Yau. On an average solve, here are my splits:
First 2 Centers: 4-5
3 cross dedges: 7-10
Rest of centers: 8-10
Rest of edges: 10-20 (Varies a lot)
3x3: 10-20 (Depends on Parity)
What do I need to work on the most?
While I'm slower than you are, I think that you should work a bit on bringing the rest of centers to 6-8, and the rest of edges to 8-17. Also, try and see if you can get rid of OLL parity during center building(it's hard, but some people can do it).
I have been looking for all advanced cases for f2l in BR slot, but can't find a site which providing all things I want,
can someone please help me?
Just use the same algs you'd use for FR/FL, just mirrored in some way.