Refurbishment refer to recycling something that r not in use or bad condition into another thing that could be more useful Renovate and Repair r pretty close and not really sure how to explain it.

Repair means fixing something in a bad state and the least related one with the others. On the other hand, refurbish and renovation are fairly close and can often be used as synonyms though if there's any difference that would be the fact that renovation being a broader term then refurbish you can refurbish and renovate your home but refurbishing doesn't extend to structural changes, means only painting the walls, decorating again, changing the furnishing etc meanwhile a historical site can be renovated.