Extremly low quality shadows on the highest quality

Hey! I have no idea what is going on, and why the shadows are so pixelated..

 

Your spot angle is way too high. Due to how projection works this causes an uneven distribution of pixels in the shadow map, essentially wasting more pixels on things closer to the edges of the frustum. Try switching to point lights instead.

 

It's still gives some weird shadows :\
and if i use HDRP i lose like 100 fps just for using it.

 

A shadow casting point light is roughly 6 times as expensive as a shadow casting spot light, and Unity’s point light shadows are kind of terrible.

However what you’re seeing is the expected result of using hard shadows. You’re seeing the aliasing in the shadow maps, which is unavoidable when using Unity’s built in shadows. Soft shadows, or something like the NextGen Soft Shadows asset will blur the shadows to hide the aliasing.
https://forum.unity.com/threads/nex...ed-dynamic-penumbra-shadows-for-unity.440088/

For sharp shadows you’d need to use stencil shadows (which I don’t know of a working implementation for any modern versions of Unity), or raytraced shadows, which are currently only available for an experimental branch of the HDRP and only for Nvidia GPUs.