before D2 there was only a wire , and before D1 there was a 50 k resistor but the output was very very badly distorted, so i figured i could switch the wires with diodes to add a little stability and symmetry, and it did, except the output isn't so sine wave, i want to know what I should change to make it a sin wave and also what is this shape of wave called and how to control its amplitude by which resistor? or is it the input of the positive side of the op amp?
EDIT: I lowered the input of the positive input of op amp, the output was a half sine wave, only positive side can be seen, what does this mean?
The circuit in the original drawing was taken from here. Additionally the operational amplifier used is one of this type. Your version uses an old 741 type operational amplifier which I am sure AG will point out is over 40 years old. The original design uses an op amp that is Rail to Rail. There are major differences between your 741 and the FAMILY OF 600μA/Ch 2.8MHz RAIL-TO-RAIL INPUT/OUTPUT HIGH-DRIVE OPERATIONAL AMPLIFIERS used in the original drawing. I have no idea what you changed the design for other than it wouldn't work. Also, why you added an oscillator to the circuit? The original circuit concept is explained in the link.
<EDIT> If you want to use a 741 remember the upper frequency limit is about 1 MHz. I suggest you look at circuits like this one and also a Google of LM741 Wein Bridge Circuits will bring up additional results.
It is an ordinary Wien Bridge oscillator from a Texas Instruments document about sinewave oscillators.
Usually a low distortion Jfet is used to control the amplitude. A long time ago a light bulb was used.
The circuit I show uses two diodes to soft-clip the signal when it becomes too high in level.
Soft-clipping adds distortion but it is not too bad.