Image mosaicking, clipping, reprojecting and exporting as tiff to Drive using GEE.

Image mosaic is a technique that combines several images with overlapping parts (the images may be obtained at different times, different viewing angles or by different sensors) into a large-scale seamless high-resolution image.Clipping is basically editing the image to the area of interest, while re projecting is changing the coordinates to fit the AOI.

I will show you how to perform these procedures using Google earth engine .

// Imports
var s2toa = ee.ImageCollection("COPERNICUS/S2"),
    geometry = 
    /* color: #d63000 */
    /* shown: false */
    /* displayProperties: [
      {
        "type": "rectangle"
      }
    ] */
    ee.Geometry.Polygon(
        [[[0.7157895807873604, 49.2914621860271],
          [0.7157895807873604, 47.7784732314115],
          [4.31930520578736, 47.7784732314115],
          [4.31930520578736, 49.2914621860271]]], null, false);
// Create a geometry representing an export region.
Map.centerObject(geometry);
var s2 = s2toa.filterDate('2020-04-01', '2020-06-25')
.filterBounds(geometry);
//print(s2);
var image = s2.mosaic().select('B1','B2','B3','B4','B5','B6','B7','B8','B8A','B9','B10','B11','B12');
//print(image);
var vizParams = {'bands': 'B8,B4,B3', 'min': 0, 'max': 4000};
Map.addLayer(image.clip(geometry), vizParams);
var reprojected = image.clip(geometry)
    .reproject('EPSG:32632', null, 10);
//Export image to tiff
Export.image.toDrive({
  image: reprojected, 
  description: 's2_UTM',
  scale: 10,
  region:geometry,
  maxPixels: 6000000000
});

This should be the end result