Suppose that I bought an old house, and changed walls and windows, repainted the house, used new wallpaper, bought new sofa, table, etc... For this kind of thing, which word is more appropriate, "decoration" or "remodel" or "upgrade"?
In this context:
Restore = 1) Make major repairs to a severely deteriorated building, or 2) Return a building to its original state (for example, by converting a house back to single occupancy after it has previously been turned into separate apartments, or by replacing original features of its design or decoration).
Renovate / upgrade = Make significant improvements to update a house or to maintain its infrastructure in good condition, e.g. by rewiring it, replacing worn-out plumbing or fixing sagging floors.
Remodel = Make significant changes to the layout of a house, possibly in combination with renovation or restoration work.
Decorate / redecorate = Make cosmetic improvements to the interior of a house, such as with paint or wallpaper.
As you can imagine, with any specific building project it can be hard to define where the boundary that separates (say) renovation and restoration, or remodelling and (re)decoration, lies.
Restore , renovate or remodel may describe what you want to do. Restoring your house you may upgrade it ( adding, for instance, an air-conditioning system) . Decoration refers more to internal works to make in more attractive and comfortable.