Gentlemen, I'm sorry I did not thank you immediately for your suggestions. But I could not get more memory in Armbian.
On the box from the bottom:
Mele model A2000G .
After a few hours of fighting, I opened the box. I found memory chips on the PCB.
MT29F32G08CBACA FLASH 4GB MLC
2PCS X H5TQ2G63DFR-H9C DDR3-1333H (supports down binning to DDR3-1066F), x16, density: 2G
That means I have 4 GB of flash and 512 MB of RAM even though I have an A2000G sticker on the box. Thanks for support . Igor, you're doing a great job.