I'm new to blender, so sorry if my question sounds dumb. I was following tutorial, and built this model:
After building it, I was trying to render. Because I'm on mac laptop, so of course the render turn out very shitty.
But the most confusing thing is after this, my viewport became the same low quality as the render image.
My render mode is on Eevee.
After receiving answers, I was able to find viewport shading in look dev mode. But in rendered mode, I could not access.