Instagram downscaling uploads

[Mehow Malachevskee]

Huawei P20
Whenever, I upload a HQ picture it downscales the quality of my photo. My photos come out grainy and fuzzy.

I tried this same step on my iPhone and there was no quality loss on the upload.

Any idea why this might be happening?

 

[ManiacJoe]

How big in pixels (length and width) is the picture?