I prefer smaller phones and currently use an iPhone 13 Mini which I plan on using for another 3 years. Sadly the battery keeps on dying and I'm on my second battery. I prefer repairing myself since most of the local shops provide lower quality batteries and I'm a bit paranoid of leaving phone there. My screen is also broken and also the back glass. I'm thinking of ordering few replacement parts from Aliexpress and was wondering if there are any good resources to learn other than phone specific guides on ifixit.
Messing with iShit can be very exhausting because everything is locked, you are got to have some really expencive programmators from your local wizards to move towards repairing those.
I am amused of why are you opening the thread with expressing your love to smaller phones, not your love to soldering under microscope and messing with BGAs and repairing all neighbours' Nokias after your school classes, so I am almost sure you are a wrong person to do this kind of job no matter how hard you will try.
Don't afraid of leaving your phone into hands of professionals, they typically have too grinding schedule to read your iCloud files or harm you using the hardware vector.