Greetings @AVIStudio!
Your issue description sounds like a culling problem, your grass is not being rendered at the desired distance. The foliage guide from dev community states the following:
Foliage instances are rendered as clusters in a single draw call and each cluster is either rendered or not rendered based on occlusion. Setting a value in the End Cull Distance parameter in the foliage details causes the clusters to be culled beyond that distance. However, this will cause groups of meshes to disappear abruptly as the entire cluster goes out of range.
This can be reduced by adding a Start Cull Distance parameter and then setting up the Material appropriately. In the vertex shader, a per-instance fading factor is calculated, which goes from 1.0 at the start distance to 0.0 at the end distance. This is accessible in the Material using a PerInstanceFadeAmount node. When connecting that to an opacity or masking value, you can use it to fade instances over a distance before they reach the Cull Distance End and are removed from rendering. Lowering the value of the FadeMultiplier parameter will increase the speed of the fade. A value of zero will make your foliage invisible at any distance.
The example Material below multiplies the Material mask by the fading factor to thin out the foliage mesh’s leaves until they completely disappear.
You can check the full guide here: