Hi @maro ,
you can use the partition guide to give you an idea about partitioning, although not intuitive as you say; it does offer an insight into how to partition!:
PLEASE NOTE: THIS GUIDE DOES NOT DEPICT THE INSTALLATION (CREATION) OF A UEFI PARTITION. IF YOU HAVE A COMPUTER WITH UEFI/BIOS, MAKE SURE YOU ALSO CREATE A UEFI/BIOS PARTITION AS WELL. SEE FURTHER REMARKS ABOUT UEFI PARTITIONS IN THE GUIDE!.
Linux beginners should also look here:
You can only partition on an unmounted drive using an installation disk of your Linux flavour with a partitioning tool included, use the Gparted tool in live mode, or you can download a copy of Gparted from the link…