The Lenovo 100S is a good little laptop, but it has one drawback, as Windows has continued to bloat, the onboard solid state disk drive of 32GB (in reality 28GB) has become increasingly inadequate, with e.g. Windows updates no longer being able to be installed. One method to work around this, until the bloat gets too bad, is the following:

Note: I cannot guarantee the performance of your system after these changes, but at least it will work

1. Install a Micro SD card in the slot.  Up to 64GB is officially supported, but people have reported using more than double that, I am using 32GB.

https://psref.lenovo.com/syspool/Sys/PDF/Lenovo_Laptops/ideapad_100S_11/ideapad_100S_11_Spec.PDF

2. Move Dropbox to that card:

https://www.dropboxforum.com/t5/Apps-and-Installations/Move-Dropbox-folder-to-removable-drive/td-p/43533

3. Move the system pagefile to that card:

https://top-password.com/blog/change-disable-or-move-pagefile-in-windows-10/

4. Change Chrome (and any other browser) and Windows system Downloads file location to be on the D: drive.  Do the same for any other folders you use, e.g. pictures, videos etc.

4. Hopefully you now have enough usable disk space!