I think that maybe the language barrier you mentioned is preventing complete understanding here. Let me try to help, if I may.
No, there is no definite link between Hep-C and brain fog, There is also no direct-link between HIV and brain fog. Some people who have either or both may get brain fog, but that does not mean that you will. Anyone who tells you otherwise is wrong. Don't be scared by such reports and don't even think about committing suicide because of something you read on the internet!
Now, Luella May has pointed you towards a very good protocol for Hep-C
I know that the protocol is a good one - because I researched and wrote it.
One of the key supplements listed in the protocol Sutherlandia OPC is also excellent for HIV, and thus the Hep-C protocol should be good for both of your conditions. For the HIV, adding olive leaf extract might be a very good idea. There have been reports of HIV being totally eliminated with the use of olive leaf extract.
OK, that is it. You have an explanation and a solution. Stop worrying my friend! Decide on a good protocol and lifestyle and embrace life and good health.