I am brand new to linux and have decided to install Manjaro onto my laptop alongside windows 10 after trying ubuntu MATE out on a really old laptop I had lying around. I was having a ton of issues with the initial boot into the flashdrive that I put the manjaro iso onto using Rufus where I would get in error in the grub bootloader saying "filesystem unkown." I researched heavily until I could boot into the flash drive and install, and finally was able to boot into it after installing different iso's and trying to correctly put the iso onto the drive, changing the boot from UEFI only to UEFI and CMS (which every video and forum post I read said to use UEFI only, so not sure why the opposite worked), and selecting to boot from the "Sandisk" instead of trying "UEFI Sandisk."
So after finally getting into Manjaro and making sure everything seemed to be working before installing, I began the partitioning process. My laptop has an SSD which is where my windows boot and an HDD for mostly everything else I install in windows. I planned on putting Manjaro onto my HDD, so I made a partition for swap after shrinking my HDD for free space and then made the main "/" partition for Manjaro. The I clicked next and finished the process until it said installation failed and gave me a bunch of lines that seemed to be referring to the bood loader, so I did the partitions again, just removed the ones I just made and re-made swap and "/" but this time I chose my HDD instead of my SDD (since I figured thats where I am installing Manjaro) as the boot loader installation device.
Installation was successful and I restarted PC, only to find it booting straight into windows without giving me the option to chose which OS to boot into. I plugged back in the flash drive wih manjaro iso on it after unplugging it once the installating process finished, and chose to boot from "Sandisk" again like I did when booting into Manjaro for the first time. There were also two options for windows boot manager and then an "UEFI Sandisk" option, which either took me into windows, or the same grub error screen I saw when trying to initially boot using the flashdrive. It took me into the Manjaro screen that I first saw and this time I went to the bottom and selected "Installed BIOS System on hd1,gpt5", and I believe that is my HDD that i installed Manjaro on. Tt took me to the grub screen where I select the OS (I think, because it proceeded to automatically boot into my Manjaro log in section before I could read the screen). Everything seems to be working fine, but I am still pretty confused as to why the only way to get into my Manjaro OS is through the USB... Any help is appreciated.