What am I supposed to do with mail and medical forms? / what works for you all?

Cleaning my house this morning and I found several envelopes, which I put into our box of mail, and then I realized that once mail goes into the box it NEVER gets opened - box is in a central location and is visible. I like that the mail is all in one place but clearly I am not addressing it lol. Hopefully there’s nothing important in there. Also found were several medical forms which I feel like I should keep but no idea where to put. I often need to refer to old medical stuff, like prescriptions, or my vyvanse receipts, and can literally never find them, so i am doing something wrong for sure.

How do you guys make sure mail gets handled, and where do you put mail, medical forms and receipts in order to not lose them but also deal with them?

Bonus points if you can tell me exactly what you do with each type of mail, because I think my problem is 90% of mail i have no idea whether i should keep or toss it.