Can someone Help me? (host files)

can I make a free website where I can save files and give them back in processing on the mobile phone?

Hello,

Some details would help.

Initial thoughts:
https://www.hostingadvice.com/how-to/best-file-hosting-services/
12 Best Free Website Hosting Compared (2021)

I have also set up a “home” server on my personal PC in the past.

:)

and how can I combine something like that with processing?

Do you need a database like thingy to store some data and retrieve from your sketch when you need it?

If that is the case then you should look into this

yes but i don’t know how to upload / check files

I personally use MongoDB in my javascript projects. It has enough free features for a beginner. But you can find the getting started page for JAVA here. Hope it helps!