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 https://openwrt.org/supported_devices/432_warning 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.