How can I restore openwrt to factory settings? Including the password. I tried "Factory data reset" from settings but it didn't help.
You can ssh "rm -rf /overlay/*" without the quote, if you do not know how to you can flash your device with topic HOW TO FLASH ZIDOO X9S UNIT with 1.2.7 image.
is any possibility to extend space on /overlay because it's only 37MB (Linux OpenWrt 4.1.17-g9100299-dirty #90 SMP PREEMPT Tue Jan 14 12:18:18 CST 2020 aarch64 GNU/Linux) x9s (OpenWrt 19.07.0-rc2 r10775-db8345d8e4 / LuCI openwrt-19.07 branch git-20.115.52331-39a8290)