Yes,you can have them reshaped in optical store.Go to ask your nearby optical store.Some opticians may be unwilling to do this because it takes much effort and doesn't worth it.so it is not recommended to change the shape.
Yes,it is possible to make them smaller,but you are not recommended to do so.Because the finished shape may not satisfy you and it takes much effort to do it.If not made properly,the optical center may get deviation and affect your vision.
Now that your current lenses are too big, so technically it is possible to cut them small. However, most labs are unwilling to do it because when they cut the lens to meet your size, the lens won't match its original frame. As a result, you might not like the end result.