AR750S is speed bottleneck for wireless

I have a 2012 year old MacBook Air running MacOs 10.12.8 I am starting to stream using ATEM Mini Pro hardware but I may need to use 802.11 wireless if the venue does not have a hard wired connection. I was worried about the speed of the wireless on this older laptop so I thought connecting high speed wired eithernet to the GL.iNet AR750S and using its wireless would be a good solution. I figured the newer chip sets plus using either the 5 GHz or 2.4 Ghz wireless etc.

Long story short I added the Thunderbolt Gigabit Ethernet adapter to the MacBook air and connected the GL-AR750S-EXT via cat 6 cable. Set up was easy and soon I was testing on my home network. I have a very high speed connection to my ISP. I tested Internet speed both though the laptop 802.11 and through the AR750S. Here are the results of

Macbook air internal 802.11 wireless 133 Mbps down / 115 Mbps up
Macbook ethernet to AR750S wireless 25 Mbps down / 18 Mbps up
I tested a few times to make certain I did not have an anomaly. The results were consistent.

Any idea why the Wireless Internet is so much slower through the router ?
Is there anything you could suggest to improve the speed?

To make it clear, you are connecting Mac Air to AR750S with cable and connecting AR750S to your wifi as repeater?

When setting up AR750s are repeater, you have choice to repeat on 2.4G or 5G. Seems you are repeating on 2.4G so 25 Mbps is normal. Pls repeater on 5G and it should be much faster.

But 133 Mbps on mac air is pretty good.

I have 2012 Mac air and its wifi is really bad. The main problem is unstable and connection drops. But if you can connect and get a speed it should be OK.

Yes connecting the Mac air to AR750S using an Ethernet cable and using the router WiFi ( turned off mac air WiFi )