bandwith test - optimize link

HI
I have a 5Ghz Link, over max 0,5 - 1 km and I wil like to optimize it 110%

If I run bandwith test
RX is 26.8 Mbps
TX is 27.0 Mbps

both
RX 20 Mbps
TX 6 Mbps

I use Integrated Router Antenna with rb112 board
There is a signal strength -55

Is a 20Mbit fiber connection, and I will like to get all 20MBit over the the link or maxium transfer. I want to get som input how to trim it 110%
if I bandwith test two rb532 with cabel is max is 100Mbit
And I only have 20% here is to bad, is my head point

hope someone can help