as you can see on the picture (accidentally switched to ormmaterial3d on the screenshot because i was trying things that time but lets pretend its the standardmaterial3d )when i used the albedo it gave me this awful look of the building, it doesn't mix well with the moss on the walls, also i was wondering how do i use this opacity image texture on the folder on the lower left (this asset is downloaded from sketchfab)

You have to go into the mesh instance (on the top of the right hand inspector panel) and expand the meshes. Then look for the model that is for the grass.

In the material parameter you can select transparent or alpha scissor. Note, this costs performance, so you don't want to do it on the whole object, just on the parts that need it.

    cybereality it actually came from this website. i downloaded the obj format so in the zip i only have one obj which is the house itself and then the texture images

    Oh yes, I had that issue too. I'm not sure if there is a way to fix it.

    Import to blender or other DCC first, then make any adjustments necessary before exporting to glTF or FBX.

      Megalomaniak i remember it having gITF version in the downlaods, i just chose obj cuz its the most familiar one to me

        The glTF works fine, but it's only alpha scissor transparenct (1-bit) since there is only one texture. So it doesn't look as good as the render on the site.