Apple air iPad 2 ,s Wifi very slow what is the reason. Showing speed 120 mbps but iPhone 7 Wi-Fi show speed 360 mbps. What’s the reason?

You think 120 Mbps is slow?

I pay for a 50 Mbps plan of which my download speeds average between 60-70 Mbps.

You are getting nearly double that speed!

Many factors affect WiFi speeds. It maybe the age of your iPad, the Wifi specs of the device, how many other wireless devices are occupying/using your home network, Internet/online traffic, lots of variables.

Your iPad Air model will be 7-years old, this year.

No.

A 2014 iPad Air 2 will soon be 7-years old, in 2021.

It doesn't matter when you purchased. That iPad model is a 7-year old device.

I already gave you a bunch of reasons and explained that there maybe even more variables.

Online Intenet traffic is a HUGE variable in WiFi Internet speeds, no matter what data speed plan you purchased.

You could try manually setting up of your WiFi settings using these DNS server addresses instead.

Quad9 (recommended)

9.9.9.9

149.112.112.112

2620:fe::fe

2620:fe::9

OpenDNS

208.67.222.222

208.67.220.220

2620:0:ccc::2

2620:0:ccd::2

Cloudflare+APNIC

1.1.1.1

1.0.0.1

2606:4700:4700::1111

2606:4700:4700::1001

Good Luck!