ARKSNT wrote

The TL-WBS210 is connected to the Modem Router of my Internet Operator in ethernet, and when I set it as a repeater all my network becomes unstable.

If you set repeater mode, it uses the wireless network to connect to another wireless network which should be extended in its range. If you connect the WBS to your ISP's modem/router by Ethernet at the same time and wireless network is also connected to this network, you create a loop. Makes no sense, can't work this way.

If you want to extend the range by connecting the WBS210 to the ISP's router using cable (the most reliable way), use either AP mode or AP router mode. See Chapter 2, "Operating Modes" in the WBS210 User's Guide for more information.