Drilling into mineral plasters/house facade

Hello everyone, we have a timber frame house with insulation and mineral plaster on top. Now the house number lighting on the facade needs to be replaced (see picture). Here are 2 questions:

1. What should be done with the old holes in the wall? Should they be sealed with, for example, silicone?

2. How is the best way to attach new lighting? Gluing? Drilling? If drilling, are there special drill bits/anchors/screws for such walls?

Thanks! Ashley

The holes should be filled either with facade sealant based on PU or with a trowel of plaster with a similar structure. Silicone is unusable outdoors. Ask a painter nearby who also does plaster work. They often have leftovers there.

New attachment with special insulation anchors. Google it, it looks like a conical screw made of plastic.

The windowsill is very durable on the outside. But not paintable, in my opinion that is the biggest disadvantage of the sill. Adhesion strength and UV resistance are excellent. Also good is MS Polymer, very adhesive, very UV resistant, paintable. Or take a tube filler for outdoors. Available.