Not enough info for a categorical answer. Earlier comments list some of the unknowns. (E.g. is this on BIOS or UEFI? Are you using MBR or GPT partitioning?) I can only make general comments and recommendations, such as: get some Linux experience yourself before trying to do something like this. Install the desktop OS and use it as your main OS for a few days. As for partition sizes, my general guidelines are: root (/) 32GB, 64GB if you will add a lot of additional software. Swap at least as big as RAM, and ideally 2x RAM. Then the /home partition can be as big as all the remaining space, leaving a reasonable amount for Windows. (E.g. making sure the Windows partition has at least 75% free space.)