1. Make sure your bootloader is unlocked!
2. Once you're unlocked enter the following ADB commands to extract your current boot image (Your phone needs to be on)
adb shell dd if=/dev/block/bootdevice/by-name/boot_a of=/boot_a.img
adb pull /boot_a.img pathinyourpc
4. Put the boot_a.img file on your phone
5. Open the magisk manager app and click the "Advanced Settings" button, then enable "Prserve AVB 2.0/dm-verity & Preserve force encryption", then select the top "Install" button and select "Patch to boot image" and select the boot_a.img
6. Now magisk will create a magisk patched boot image file, put that on your computer
7. Now enter the following ADB command
adb reboot fastboot
fastboot boot pathtomagiskpatched.img
Congratulations you've now successfully rooted your phone!