I wrote a few (never published) novels after graduating from university, it's very rewarding but takes a lot of discipline and perseverence. I wrote genre fiction, so very different to you, but my memory from around 10 years ago is that publishers expected novels to be a minimum of 60k words - anything less than 50k was pretty much out of the question. Since you're asking such a specific question, I'm assuming you're at least considering sending it to publishers, otherwise it can obviously be any length you like.
If I can offer some advice from someone who has completed writing a few novels, there are two particularly difficult stages to writing a novel. The first is literally the first word: I doubt anything else you write will be agonised over quite as much as how you start. With this in mind, I'd encourage you to remember that you're only writing a first draft: if you are serious about publishing, you'll want to revise your book over and over again, get some people who'll be brutally honest to read it, then revise again. No matter how great you think your first draft is, it will always need to be improved: many times I thought I had reached my final draft, let some people read it, got critical feedback, was grumpy and in denial about it for a few days, then realised they had a point all along (and sometimes it's not the point they were intending - feedback isn't always right, but can help you see things from a different perspective and improve your work in other ways). To get back to the point, the first word and sentence in your initial draft aren't worth a damn, just put something down to get going - you can, and probably will, change it later.
The second most difficult stage is the middle. Once you've got your first word down, if you're anything like me, the excitement of getting your story into motion and letting the ideas out of your head will carry you for the first week or two. Similarly, the final stages of writing a novel get a lot easier because your goal is in sight. The middle, though, can be a slog and where you'll really need to keep focus. There's no easy answer to this, but sticking rigidly to a routine will help. Definitely don't go more than a few days, certainly not a week, without writing: I have a half-finished novel on my laptop right now from just after the pandemic, which I was enjoying writing then went on holiday for about ten days and lost all my energy to continue. I've added bits and pieces since, but it always feels like yesterday's news when I go back. Make everything as predictable as possible: write in the same place, at the same time, and either for a set period of time or a set number of words. You can always write for longer or add more words, but make sure you at least hit the targets you've set.
Next, and this part is subjective because I've spoken to many other writers who write in completely different ways, I never, under any circumstances, edited my work in the middle of a draft. For me, if I started doing this, I'd become obsessive over making everything perfect, or realise I wanted to take the story in a different direction and need to go back and change previous chapters, making a mess of the whole thing and my mindset. Even if there's something you're unhappy with or something big you realise needs to be changed, just keep going. In the latter case, I'd continue writing as though the big change had already been implemented, then go back once the draft was completed and edit the earlier parts to bring it together. A big advantage to editing full drafts rather than individual passages or chapters is that you're considering the work as a whole rather than small constituent parts. Thus, while you'll still make adjustments to the prose and other details, having that big picture view keeps you from getting too bogged down in minutiae and lets you see each change you make in the context of what it means to the whole, rather than just how you feel in any particular moment.
Finally, write in a style which suits you rather than trying to adapt to what you think constitutes good writing to others. After being rejected countless times by publishers, I got hyper-fixated on making my prose incredibly tight and precise, without a word to spare, which made me enjoy the writing significantly less and made the work itself read far worse than the earlier drafts, becoming incredibly stilted and characterless. It's about finding a balance between being able to adjust and improve within the style which comes naturally to you, without losing what you enjoy about writing in the first place.
And with all that unsolicited advice, here's hoping some of it is helpful and wishing you the best of luck with your writing!
