Could dual boot your laptop or run windows in a VM as someone suggested. Onlyoffice was what finally solved the office compatibility problem for me during school. O365 is online anyways and works on Linux...
Replaced gboard with a FOSS keyboard without internet access on your phone? I use and like AnySoftKeyboard.
Are you on stock android or a privacy friendly ROM? That'd be #1 on my list. I use grapheneos on a pixel 8 and would recommend. Whether you have google apps on your phone or not they have access to everything you do on stock android 🤷♂️
Either way I think its important to recognize how much you've already done, and not stress about what you can't change yet. You're already more private than 99% of the general population and you aren't in school forever. I was in the same boat with a windows partition on my laptop for a couple windows only programs for school (online test invigilation can be a bitch for compatibility, windows in a VM generally doesn't work I found), but school ends and that partition is gone now.
TL;DR
You're doing good, don't stress if you have to keep some stuff around for school, give onlyoffice a shot, look into privacy friendly ROMs for your phone.
I know some folks who have problems running onlyoffice- apparently LibreOffice is the fork/spiritual successor to it. Haven’t used it a lot but so far it’s run decently.
When you’re in school you’re often stuck with the software they require. No harm in that. Once you’re finished with school you can reevaluate. If you want to be more privacy focused you could make sure you’re only using Gmail for in a Firefox container tab for instance or look into sandboxing it other ways.
For the same reasons don’t worry about keeping Windows on your computer for classes. It’ll get easier when you’re out of college, any job will give you work equipment with the software and tools they make you use and you can keep all personal information out of those. You’ll be able to use what you want on your personal items.
Privacy is important, but not important as passing your classes.
Run Linux as your host operating system and run Windows in a virtualized environment such as VirtualBox. That's how I made my transition. I was Windows only and barely started playing with Linux. Then I installed Linux entirely and put Windows on a virtual machine. And now I don't even have the Windows virtual machine anymore.
For the laptop, you can leave it with Windows but don't use it for anything except what requires Windows (e. g. don't use social media or store private photos on it). If you use it very often, consider dualbooting.
For your phone, make sure you use a custom ROM. If you need Google apps, there's stuff like microg (sandboxed Google apps that are either pre-installed in the ROM or you can add it to a ROM that doesn't come with any Google apps by default). Regular Google apps are very invasive and stock ROMs are even worse because they have their own telemetry. But I wouldn't recommend using obscure ROMs (especially unofficial builds).
There can be an issue with banking apps though. Recently Google replaced old SafetyNet system (which checked the system for root and unlocked bootloader) with a new one called Play Integrity. The problem with it is that 99% of custom ROMs can't fully pass Play Integrity so apps which require it (mostly banking and government apps) won't work. Also Snapchat and WhatsApp started banning custom ROM users recently. The only reliable way to avoid these issues is to have 2 phones: one on stock unmodified ROM (for banking apps and other things that require Play Integrity pass) and a degoogled phone with a nice reliable custom ROM (LineageOS and GrapheneOS are my recommendations but you can look at other ones like crDroid if you want more customization features). It can be a bit inconvenient but that's what you probably need if you want really good privacy
This is what I think: You cannot be 100% private, but you can be 95% private. Most of the tracking I want to avoid is from websites, mail and my devices OS.
With ublock origin in advanced mode, thunderbird + Protonmail, Linux (I'm dual booting and also have a windows VM for the things not working on Linux) and a VPN I can reach a satisfying amount of privacy without wasting too much time and effort. I'm also hosting an unfederated matrix server for private communications but I rarely use it.
To have better privacy than this I'd need a lot more effort, but the return wouldn't be big enough, so I'm good. The only other thing I'd like to do is switching to a phone with grapheneOS or something like that.
I use linux on my desktop and laptop and dont own a running copy of windows at this point. I‘m switching from iPhone to rooted OP6 with postmarketOS atm and I host my own cloud, music, tv, websites, social media, etc.
My goal never was privacy but ownership of my devices. The privacy aspect is a neat addition.
Some of my friends still have whatsapp so I bridge to them from my matrix server. If I need to use google tools I do so in the browser. I ditched most proprietary apps at this point.
It does lead to people looking at me funny if I say „sorry, I dont use windows“ but I dont care.
I still need to get my sonos to be owned by me but thats a future project.
In summary I would say if I need proprietary stuff for a project thats no big deal. I just make sure I dont go back to using it for other things.
You have solved what you have direct control over, the next step is things you have indirect control over like the policies of your school or government. Get engaged civically. Vote and advocate privacy in your community and to your elected representatives. Ask businesses if they will accept forms of payment which provide greater privacy than credit card like Bitcoin lightning or Monero.