DualBoot Windows/Manjaro

3 mounth ago I installed manjaro and deleted windows because I thought I had no more need of it. But now I want to reinstall it and make a dualboot with manjaro, I’ve searched a lot the Internet but I didn’t find anything. Can someone help me out ?

We’d need more info. Is bios set to uefi or legacy mode? Please post the output of
inxi -Fz

here it is :
Kernel: 5.15.81-1-MANJARO arch: x86_64 bits: 64 Desktop: KDE Plasma
v: 5.26.4 Distro: Manjaro Linux
Type: Laptop System: HP product: HP Pavilion Laptop 15-eh1xxx v: N/A
Mobo: HP model: 88D0 v: 78.31 serial: UEFI: AMI
v: F.22 date: 07/11/2022
ID-1: BAT0 charge: 36.6 Wh (100.0%) condition: 36.6/36.6 Wh (100.0%)
Info: 8-core model: AMD Ryzen 7 5700U with Radeon Graphics bits: 64
type: MT MCP cache: L2: 4 MiB
Speed (MHz): avg: 1412 min/max: 1400/4370 cores: 1: 1397 2: 1397 3: 1427
4: 1614 5: 1397 6: 1397 7: 1397 8: 1397 9: 1397 10: 1396 11: 1397 12: 1397
13: 1397 14: 1397 15: 1397 16: 1397
Device-1: AMD Lucienne driver: amdgpu v: kernel
Device-2: Chicony HP Wide Vision HD Camera type: USB driver: uvcvideo
Display: x11 server: X-Org v: 21.1.4 driver: X: loaded: amdgpu
unloaded: modesetting dri: radeonsi gpu: amdgpu resolution: 1920x1080~60Hz
API: OpenGL v: 4.6 Mesa 22.2.4 renderer: AMD Radeon Graphics (renoir LLVM
14.0.6 DRM 3.42 5.15.81-1-MANJARO)
Device-1: AMD Renoir Radeon High Definition Audio driver: snd_hda_intel
Device-2: AMD ACP/ACP3X/ACP6x Audio Coprocessor driver: snd_rn_pci_acp3x
Device-3: AMD Family 17h/19h HD Audio driver: snd_hda_intel
Sound API: ALSA v: k5.15.81-1-MANJARO running: yes
Sound Server-1: PulseAudio v: 16.1 running: yes
Sound Server-2: PipeWire v: 0.3.61 running: yes
Device-1: Realtek RTL8852AE 802.11ax PCIe Wireless Network Adapter
driver: N/A
IF-ID-1: enp4s0f3u2 state: unknown speed: -1 duplex: half mac:
Device-1: Samsung Galaxy series misc. (tethering mode) type: USB
driver: rndis_host
Report: This feature requires one of these tools: hciconfig/bt-adapter
Device-2: Realtek Bluetooth Radio type: USB driver: btusb
Report: ID: hci0 state: up address: N/A
Local Storage: total: 953.87 GiB used: 50.91 GiB (5.3%)
ID-1: /dev/nvme0n1 vendor: SK Hynix model: BC711 HFM001TD3JX013N
size: 953.87 GiB
ID-1: / size: 928.86 GiB used: 50.91 GiB (5.5%) fs: ext4 dev: /dev/nvme0n1p2
ID-2: /boot/efi size: 299.4 MiB used: 312 KiB (0.1%) fs: vfat
dev: /dev/nvme0n1p1
ID-1: swap-1 type: partition size: 8.8 GiB used: 0 KiB (0.0%)
dev: /dev/nvme0n1p3
System Temperatures: cpu: 36.0 C mobo: N/A gpu: amdgpu temp: 31.0 C
Fan Speeds (RPM): N/A
Processes: 326 Uptime: 1m Memory: 14.96 GiB used: 1.71 GiB (11.4%)
Shell: Zsh inxi: 3.3.23

After installation of Windows, you need to reinstall Grub2.