Hi, I didn’t see the answer if you only have your pc and no other big storage :
If you still have the installation usb or recreate one. Boot on it then you open gparted with that you remove the two partition off windows, the main with the system and the recovery one (if there is) but don’t touch the first or last partition esp if it exits. Then you can expand the partitions to get the free space. Extend to the right is fast but extend to the left can be really slow and prone to failures.
I case you Linux partition are all on the right you can also create new main partition, do the install of the linux on this one, then reboot on the USB, move the user and configuration files on the new system, delete old installation partitions, then extend the new install to take the full drive.
There is commands to remove the old esp entries I don’t remember yet.
This can take few hours so be patient.

The other option with a backup (dd) of the main partition is obviously safer but take nearly the same amount of time and need an external drive.

Gentoo obviously :
To install, easy just get this iso, with no GUI, then whip your hard drive, create partition, copy the Linux core, config your core based on the hardware technical details of every components you have and will use, compile it, add extra core drivers, compile them, add all the software you’ll use to get a GUI (Desktop environment), compile them,. Now you can finally restart without usb stick! Add all the software, configure and compile them. And for every update of every software you may check the details to be sure it doesn’t break your config.
Easy no? It just took you a month to get all the steps right!

Un deux trois… Mille ! In French (France 🇫🇷) 1000 before lips touch.

… Soixante-neuf, septante ! In French (Switzerland 🇨🇭) 70! (in France it’s soixante-dix 😂)

I use Feed the beast app, on MX-Linux (Debian based), launching the modpack “All the mods 10” run perfectly, while running the server on the same time (just need a lot of Ram)