Whether injecting vitamin B6 per week can help to reduce LDL and tg and increase HDL along with regular walking or not. (in my age)?

Don't inject. I'm sorry someone suggested B6 injections. That can actually make you sick if they don't know what they're doing. If you're the kind of person who'd actually consider B6 injections over diet, exercise and meds for lipids at your age, perhaps you'd do well to get with an evidence-based holist / natural medicine person in your community. They'll help you sort out what might actually have merit.
Doubtful. B6 likely not effective at reducing cholesterol. Walking or brisk exercise can reduce your triglyceride levels and boost your HDL ("good") levels.