Support for D-Link DWR-111?

I really need OpenWRT for this, but I do not know how to make a custom firmware. Please,
Can anyone help?
The link below contains all its information.

This device has only 4MB Flash / 32 MB RAM, which is too little to run an up-to-date and secure version of OpenWrt. See for details.

The upcoming 19.07 release will be the last one with support for 4/32MB devices. After 19.07, no further images will be built for those underpowered devices.

You are better off buying a new device with sufficient ressources to run OpenWrt.