If you opt for a clean install in the future, create a root partition (15-20GB) and a home partition using the rest of the space on the drive. You may want a UEFI and SWAP partition too, read the following guide about partitioning but pay close attention to it.
See also:
And one further question is, do you have all your important files on the laptop backed up? If you do, this will be good for your personal files as you won't have to worry too much about losing them!.
