Will brand matter between a rear derailleur and front derailleur? I had a crash recently that destroyed my 8 speed sensah reflex rd. I replaced it with a 9 speed shimano sora for a bit of upgrade but after 4 tune ups by the mechanic its still not right. Just so discouraged pls help. I noticed also that my rd hanger is kind of a little bent or not straight enough will this matter? Thank so much in advance...
I believe you are referring to the shifter, not the front derailleur. The shifter connects to the derailleur with a cable
Sensah Reflex is an 8 speed system with components designed to be interchangeable with Shimano 8 /9 speed.
http://www.disraeligears.co.uk/Site/Sensah_Bicycle_Components_2020_page_6.html
Probably the Sora RD is slightly better quality, not because it is 9 speed but generally Shimano have better manufacturing standards and shifting quality than most other brands, though Sensah doesn't seem to be terrible at all.
There is no difference between an 8 speed and a 9 speed RD so that part is fine. (Often a 9 speed is a more expensive part and made from lighter materials , but that's all)
Given that you still have shifting problems and have identified that the derailleur hanger is bent, it is obvious that that is the source of your problem. So find a replacement derailleur hanger, keep your Sora RD. If you can't find a replacement hanger perhaps you can straighten it, but given your mechanic has failed to do so replacement seems a better option.
https://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment