Hard or elastic adhesive for solid wood flooring, any experiences?

And the technical rules include at least a primer based on dispersion, in my opinion also a filler application.

Thank you very much. To be honest, after meticulous vacuuming, I would have intuitively applied my favorite PCI Gisogrund (diluted 1:1) based on a gut feeling (sorry for the brand name, I hope that’s okay).

As far as I know, it’s relatively universal, and I use it for pretty much everything I do in construction where priming is needed. Especially with tiles, filler/leveling compounds, and sometimes even in the area of "difficult" plastering work depending on the substrate.