Welcome at the forum, @Doidoire
First of all, there is a good tutorial for dual boot:
Usually, it is recommendable (if possible) to install Windoze and Manjaro on different disks to reduce possible interferences and potential issues. Nevertheless, dual booting from the same disk is certainly possible and used by many.
You need to reduce the Windoze partition (ideally from within Windoze) to make some space available. I would recommend to have an additional /boot/efi partition and to consider to use only a / partition in addition. If you prefer a separate /home partition that’s fine. sawp is recommended also, but this could be done either by a swap partition or a swap file within / partition.
Complete separate could be a data partition, ideally on your hdd. If you don’t put your data in /home (only link for example) then in total 30 - 40 GiB should be sufficient already for / and /home together. I would not recommend to have more partitions, you need a good reason to do so.