Lora E32 868/433 Mhz speed issue

Hello I'm new in the forum,
I have a little big problem with a Lora module : Ebyte-E32 433.
I'm using an Arduino to send and receive (witch work perfectly) they send and receive to the Lora module in Serial using this library :
https://www.mischianti.org/2019/11/10/lora-e32-device-for-arduino-esp32-or-esp8266-fixed-transmission-part-4/

I Also have the 868Mhz device.

Everything works expect that the sending time is extremely high ! it take's 125 ms for the sending arduino to send anything witch is only 8 transmission/sec.
This is not the actual time the Lora module send it's just the time for the arduino to send before doing something else (Maybe wait for the response of the module ?).
Our objectives was to approach 20 transmission/sec but right now only get 16 would be fine.

I really don't know where this delay come from, the "sleeping mode" is set as 250 ms at minimum so it's not the device that go to sleeping mode.
And the "air data rate" change's noting.
I also checked the library for "delay" function.

plz say if i'ts not the right channel for that stuff