Resolution enhancement/downscaling

How can I change the spatial resolution from 20 meters to 10 meters of Sentinel 2 image?

You can use

The first is a simple technical increase of the 20m and 60m bands to 10 meters, but without any improvement in the spatial detail.

The second is a kind of a pansharpening which tries to impute the patterns of the 10m bands into the lower resolution bands.