How can ı install to Qnap TS-109 II Nas?

Installing and Using OpenWrt
1

how can I install openwrt on my old qnap ts 109 II device? I was able to install Debian 9, but it doesn't work well?

QNAP TS 109 II
ARM-based core
SoC - System on a Chip
500 MHz RISC CPU
256 MB DDR2 Ram
8 MB flash

2

That is a Marvell Orion based system and the Orion port of OpenWrt was last released in 12.09 Attitude Adjustment. Since then the Linux kernel moved some Orion devices to Device Tree, so someone with time and access to devices could likely revive the port. There appear to be about 10 Orion devices supported by the Device Tree in mainline Linux.. None of them are QNAP NAS devices, so you would also need to determine the proper device tree for your NAS.