Is there a workout to lift your breast naturally?

No. Breast dropping is caused by loose skin and breast ligaments. There are no exercises to contract skin or ligaments.
Not really. While increasing muscle tone and bulk may provide greater support to the breast the effects on lifting the breast are minimal.
No. Sorry! your breasts simply hang off of the chest wall- no exercises will lift them up!
No. If a breast is ptotic ("droopy" for lack of a better word), the only proven way to lift the breast is via surgery. If the ptosis is mild, an augmentation may suffice (if the patient also wishes to be larger). Numerous methods of breast lifting exist depending on the degree of ptosis. I suggest consulting with a plastic surgeon for more information if you're interested.
No. Building the pecs up in the presence of preexisting sagging can contribute to a worse profile!