You will need to work on mesh optimization, because this model is unecessary high poly count, because the meshes are split up in various ways. Seems to be build in sketchup, I don't know how it handles the things, but there is surely a way to optimize that.

The front side for example is split up in almost 20 blocks, you could leave that one block.

May all not be relevant for a scene or a model, but to use it ingame with good performance things have to be optimized.