I have exactly like the one provided in the link and I checked the resistor and it's 27k ohms.
The datasheet says 72us at least after each transaction but I used 30us and it's working fine.
But the library I linked in the main post doesn't even use any delays except for one 2ms for the clear command. And when I upload the library examples, they work fine.
I want to know how the programmer do it ? How he managed to not using delays ? Where I couldn't get lower than 30us to get a stable writes to the glcd ?