Don’t know if you’ve played/heard of these, but some good short singleplayer stuff on gamepass that might fit the types of games you like and you could easily finish before then:

A Short Hike is getting added today and is something I’d recommend to anyone if you haven’t played it. Very pleasant game, and as the name suggests it’s very short, you can complete it in an afternoon.

Celeste is on there and is one of the best 2D platformers, if you enjoy those and haven’t played it definitely try it out.

Death’s Door is a top-down zelda-like, and one of my favorite takes by indies on that type of game.

Doom 1/2 are classics that are still very much worth playing and hold up well.

Mirror’s Edge is a first person platforming/parkour game, a bit older at this point but holds up pretty well.

Monster Train is a deckbuilder roguelite, which I know is a polarizing genre, but if you’re either into those or open to the idea of trying them it’s one of the best. Might not fit as a shorter game depending on how much of the stuff in it you want to do, but you could at least get a good taste for it and see if you like it.

Both of the Ori games are good metroidvanias that are relatively short.

Prey is a great immersive sim/fps/stealth game, if you’ve tried other Arkane stuff like Dishonored, or the Deus Ex games, it’s similar to those.

Both of the Psychonauts games are great 3D platformers. 2 is especially good and a big step up in gameplay, as you might expect with the time gap between them.

Tinykin is a 3D platformer with some Pikmin inspiration, where you’re a tiny person exploring a giant house, very fun if you like platforming and collectathon type stuff.