Sentinel-2 data, which you are probably trying to download, come at original resolution of 10m as described in the documentation:
You will obviously not be able to downoad Sentinel-2 at higher resolution. When you refer to “100m”, you are probably referring to the graphical scale in the EO Browser, which is not the same as the resolution.
By choosing Download image → Analytical, you can choose the “High” resolution, which should give you a “projected resolution: 10m”. If you do not see this, zoom in closer as the largest image download is 2000x2000px.
Sentinel-2 with 10 meter resolution is the best what one can get from open data.
If you are looking for an ongoing monitoring of vegetation, the only other possibility is PlanetScope data, which come at resolution of 3-5 meters (projected to 3 meters) and cost of 1.55 EUR per sq. km (per observation).
If interested in this, let us know the area you are looking for and we will send you an offer to purcahse imagery. Purchased data will be available through Sentinel Hub services in the same way as Sentinel-2 data is available.