Two sentinel 2 image mosaiking

my study area is between two sentinel2 L1C images that is remote sensed in same day. after i process images to L2A by Sen2Cor 2.5.5 with out DEM i want to mosaic two image for have a single image from my study area, for this operation i use Multi Size mosaic with Overlay this operation geometrically accurate , and how to accurate coregister with sentinel 1 image.
with regards

The GeFolki coregistration tool is (according to the manual) able to coregister optical and SAR data. But I didn’t manage to use it correctly. Maybe you give it a try and share your experiences here: GeFolki coregistration