how to get or where get stock recovery for B830?
disassembly UPDATE.APP through HuaweiUpdateExtractor_0.9.8.0 (use "unknown" profile, P7 is absent)
modemnvm1.img recovery.img size:12990464
1. Flash b830
2. flash twrp (newest Version)
3. go into recovery and set system as RW and not only read. (You will see a question about this @start of recovery)
4. push restart, restart system
5. you see a question about flash su...push yes.
6. delete set_immutable (See forum)
If your bootloader is locked. The easyst way (i think) is to downgrade and flash a unlocked bootloader with ADB (See forum).