Need help regarding stone hmi screen

Hi guys and girls, just wondering if anyone can help me getting this stone hmi screen running? Ive read the instructions many many times, and i sort of understand how it works, yet at the same time have zero idea how to do it!
I have the STVA070WT-01 model which can be found here https://www.stoneitech.com
Im testing with an arduino leonardo, or uno.
I also have a max3232 rs232 serial to ttl adapter to connect the display to the arduino. Also havent looked up what pins to connect this to yet if anyone knows.
I’d really like to learn 2 things
1/ how to send a variable to the screen to display it.
E.g arduino reads temp sensor, sends it to the screen, screen displays temp reading.
2/ if i change something on the screen and have the arduino update that variable.
E.g On the arduino i could have int name;, when i change the name on the screen it will update int name; on the arduino.
Hoping someone out there can help me on the right track, sorry i have no code to post yet, as im not sure where to start. But it seems to be sending and recieving hex to send and receive the variables.
An example in the instructions are:
To display 1234 on the variable on the screen.
A5 5A 05 83 00 20 04 D2
A5 5A = frame header
05 = command byte length (83 00 20 04 D2 total 5 bytes without frame header)
83 = write to register command
00 20 = variable address to send to on the screen.
04 D2 = Data content (1234)
Thanks, hope someone can help."