Need help with Wien-Bridge Oscilator

[purpleclover]

Greetings everyone, i have a assigment and i need to creat a wien bridge oscilator that uses potentiometers so the out frecv can be modified between (10, 14 )Khz...and the out voltage between (6,9) V ... i allready made a sketch but i just cant figure out how to do this...every time i try to make the amplitude bigger the frecvency changes and the other way around. Please, can someone help me ?