Linux is broad and deep so it would help if you gave some examples of tasks you are failing to do.

Edit: I guess I can give some fundamental topics for your search, but I don't have many resources at the ready.

For starters, many topics will apply to all of Unix, not just Linux. So make sure you understand the difference, and learn about the Unix philosophy.

Also, I think the most useful piece of documentation is the Arch Wiki. I'd always check here first. The table of contents should give you a good idea of the scope of information.

1. Filesystems. In Unix, everything is a "file". Explore the directory layout. Maybe learn about the FHS (filesystem hierarchy standard) and XDG. Learn how file permissions and ownership work. Learn about disk encryption with LUKS. Learn about GPT partitioning and EFI boot partitions. If you want to manage a filesystem spanning many storage devices, I highly recommend looking into ZFS. You might also want to set up some kind of file service like NFS or something with a web client like copyparty or dufs. Try out the dust and duf tools for checking space usage.
2. Networking. I don't know how deep you need to go here, but Linux networking is highly customizable. I think most distros use systemd's built-in DHCP client in systemd-networkd. Have a look at nftables if you want to mess with firewalls. Wireguard for VPN. Learn to use the ip tool.
3. Remote Access. Especially for a desktop, it's very useful to set up an SSH service on your PC so you can access it remotely from e.g. a laptop. You can even SSH over the public Internet using a VPN.
4. Monitoring. Install BTop to get a quick overview of system activity and resource utilization. I also like the procs tool as an alternative to ps.
5. Shells. As part of your Bash journey, I'd also check out shells like fish, zsh, and nushell.
6. Package Management. I'm not very familiar with Bazzite's package manager. It's an immutable distro, so that will make a difference. Read the bazzite docs for this I guess. You'll probably need to learn about flatpaks. I'd recommend checking out Nix if you want to try something different. I also quite enjoyed Arch's pacman if you're willing to try a new distro like CachyOS or EndeavourOS.
7. Dotfile management. I recommend learning some basic Git or Jujutsu (jj) and managing your configuration files in a git repository. You can also do this with Nix via Home Manager.
8. Desktop Environment. I don't know which variant of Bazzite you chose, but it's probably a complete DE out of the box. Just know that you can customize your DE quite a bit. I personally enjoy tiling window managers; you might want to check those out.