You can lose upto five to six kilos temporarily through Running (jogging if that is what you do), you can do more with Sprinting.
Now the problem , the faster u lose fat, less time for your body to adjust to the change in skin composition so it sends collagen fiber to make up for the change in skin elasticity, that you see as Stretch marks.
So losing 1kg per week that is 4kgs a month is a healthy goal.
Now another problem, you will lose fat only temporarily because u are just driving the car faster by moving the wheels faster, without a strong engine wheels can’t go any faster, so when u stop ur energy consumption is as low as the engine capacity of the car (ur metabolism).
A better idea is to develop the engine of a car from a nano engine to Audi engine, which will not only help u run faster and burn more fat but also burn more energy when at resting (Resting Metabolic Rate).
The way to do is to improve your strength by resistance training and gradually lifting weights to become stronger (muscle growth causes more energy burn thus resulting in higher RMR).
If you have body pain in back or knee or shoulders without any history of injury, u need muscle tightness release under the supervision of a physiotherapist and not a doctor.
Don’t be afraid of lifting weights, because your body isn’t , just your mind is. Ur muscles and bones are designed to regenerate under good stress and degenerate otherwise.
Stay strong stay fit stay happy .