Controlling DC motor with weight and set values.

I need help with the solution of my product.
Unfortunately I'm still a beginner and I don't know anymore. I wanted to create a weighing system with dosing. The principle is that I enter a value of 250 on the keyboard and the peristalist pump starts to feed the material.
When the value is reached, the pump stops and the second pump starts to dispense.
This will dispense a material that has also been entered for example 100. So the weight will know that it has to stop at 300.

I don't know how to write the condition. When the value reaches 200 stop and start the second pump that stops 100 + the first value.

I use arduino uno, the weight sensor is hx711, the L9110S provides motor control.

I attach the written code for me - #include <LiquidCrystal_I2C.h>#include <Wire.h>#include <Keypad.h>#include -

Unfortunately I got stuck and I don't know how to continue ... Thank you very much for your help.

And sorry for my english..