Don't worry, this is actually true of quite a few translators, myself included.
Actually, the game is already set up to read scenario text files if you extract them and put them in the right location.
I've attached an archive containing all the files from the June version of the game. Just unpack into the main directory (if done correctly, you should have a new "scenario_en" in the same location as "Mansha300.exe").
Do note, the above is just for the VN text, you will still need XUnity.Autotranslator for the UI text, as that is hard-coded into the game code.
(There are also game data files, for things like character names/info, skiil names/info, etc which you could edit directly. But the game doesn't include a nice facility to replace those like it does w/ the scenario files. You'd have to go through XUnity.ResourceRedirector to get those into the game. I can provide more detail if you're interested.)
I will typically have both Google and DeepL open, as they tend to give good and bad results on different things, or atleast enough of a difference that I can sus out the meaning of bad results.
I'll also recommend looking into the Sugoi offline translator model (you'll need to join their discord to get the latest version). It's trained on VN text (rather than a general corpus like Google and DeepL surely use), and I find it does a much better job on the text in these games, especially the smut and onomatopoeia.
