[操作疑難] Wifi Extender question

my router totolink 2004 is at the centre of 600ft house, after two main wall, the AC signal is zero and N signal is 5mb up / down,

If i use a wifi extender (no home plug - no extra socket ; no Xiaomi router - plan to attach the wifi extender at toilet which is in-between the two main wall), any suggestion?

target for TPLINK RE200 (AC750), if no obvious improvement on AC signal then the 850 series,

thanks for comments.