Creatinine serum 1.5 mg/dl gfr 47-nb bun test 27 how bad is this. Can there be ways to improve on these results. Thank you?

Big picture. Everybody's kidney function declines some with age. I'm good with your BUN especially if you eat a lot of protein. And if you're a mature athlete, this may even be fine; creatinine varies with a man's muscularity. When i was lifting weights daily in my early thirties, my creatinine run 1.5 to 1.6 -- perfectly healthy.
Depends. If it is acute- from dehydration, some medications, blockage or other causes involving kidneys it may be reversible. If is chronic kidney disease ( going on for some time- technically > 3 months), it may not be reversible, although there is a possibility. Careful assessment needs to be done to rule out correctable causes are found.