Unity – Free Realistic Interior & Architecture Assets for beginners?

Hey everyone,

beginner here, I'm working with Unity3D 2019.b3 for a bit now and try to wrap my head around it.
I'm trying to create a small map / area where the character is in a room (house). But also want to get into post-apocalyptic scenery:

I want to create realistic sceneries etc..
for now I'm just a beginner and want to wrap my head around game dev. and see how far this takes me thus I'm pretty sure its kinda understandable from a beginners perspective that paying for every needed / wanted asset on the Unity Assets Store, especially in the current learning state, is undesirable.
That's why I want to ask, is there maybe something like a small (or big) collection of realistic interior / architecture free assets like:

1. interior objects (wooden table, chair, carpet, books, glas, wall, arrows, etc...)
2. materials (wood, metal, blood, water etc...)
3. blueprints (not sure but like...animations, object behavior, explosions, more blood assets)

for said theme / scenery?
(optional: If possible how are these realistic assets (objects) made ? I'm pretty sure blender or 3ds max are used but I have no clue)


Any help appreciated, thanks for reading!