Hello,

> I have installed gmp 6.1.1 (with gmp.h present in the folder) and use the
> following command:

> Still it cannot find my gmp library.

You also need to instal the so called -dev packages, depending on your distro. I'm
using debian, as an example, the package to install in this case is libgmp-dev:amd64

Cheers,
David