Partitioning the disk after installing mint cinnamon

Hello there,
I installed Linux Mint Cinnamon 20 as a single OS for my laptop, erasing Windows 7. But I forgot to partition the disk. Now I want to keep the OS data and user data on different partitions. What may be done now? May I partition now without disturbance to OS files? How? Or I have to go through re-installation?

Please help me.

Regards