I want to display 2 textures on 2 squares. Here's what it looks like.

the image size is 325x325. How to make the texture of the right side more sharp.the only way to get good quality is when I use textures and objects with the same size.I'm using PNG images and the following GL methods.
My vertex

#version 430 core
layout(location = 0) in vec2 position;
layout(location = 1) in vec2 texCoord;
layout(location = 2) in float layer;
out vec2 uv;
out float layer_get;
uniform mat4 MVP;

void main()
{
   gl_Position = MVP * vec4(position.x, position.y, 0.0, 1.0);
   uv = texCoord;
   layer_get = layer;
}

My fragment

#version 430 core
out vec4 color;
in vec2 uv;
in float layer_get;
layout (binding=0) uniform sampler2DArray textureArray;

void main()
{
  color = texture(textureArray, vec3(uv.x,uv.y, 0));
}

Gl methods

    // Create storage for the texture. (1 layer of 325x325 texels)
   gl::TexStorage3D(
       gl::TEXTURE_2D_ARRAY,
       1, 
       gl::RGBA8, // internal format
       325,
       325, // WxH
       1,   // Number of layers
   );

   let img = image::open(&Path::new("y.png")).unwrap();

   let to_rgba = img.to_rgba();
   let data = to_rgba.into_vec();

   gl::TexSubImage3D(
       gl::TEXTURE_2D_ARRAY,
       0, // mipmap number
       0,
       0,
       0, //x, y, z
       325,
       325,
       1,
       gl::RGBA,                               // format
       gl::UNSIGNED_BYTE,                      // type
       &data[0] as *const u8 as *const c_void, // pointer to data
   );
}

I've also heard about mipmap, but I don't understand what it is or how it works... and how should I include it in my texture array

I also heard about Mipmaps. They are smaller, pre-filtered versions of a texture image, But I have absolutely no idea how to include it in my texture array

Okay somehow I managed to get a much better image. But I still can't figure out how to manage mipmaps in a texture array

gl::TexParameteri(gl::TEXTURE_2D_ARRAY, gl::TEXTURE_MIN_FILTER, gl::LINEAR_MIPMAP_LINEAR as i32);

Mipmaps are smaller filtered images of the original texture, a mipmap level 1 is half the image size, mipmap level 2 is quarter of the original size and so on.

This is useful for performance and image quality. Without mipmaps you will have strong visible articats in the distance due to the fact that the GPU does not downscale the original texture but rather takes nearby samples (LINEAR) with either no or small kernels (interpolated regions). You absolutely want mipmaps for textures, unless you have special cases, like a 2D game or a graphical interface.

Generating mipmaps is easy with OpenGL 3 or later. Just use glGenerateMipmap and you are good. With previous versions you may use gluBuild2dMipmaps. Of course you can also access and upload your own mipmaps but thats just more difficult.

In your case generating a mipmap probably looks like this:

gl::GenerateMipmap(gl::TEXTURE_2D_ARRAY)