I have been in quarantine for 20 days and although I prepared very well before starting it, I have found some things that I could have been done better. I hope I can help those who are about to enter or are newly quarantined.
Here is a list of the lessons that left me these first days of quarantine.
I should have frozen fresh products

The price of fruits and vegetables went up as the days went by. I should have bought quite a bit more and kept in the fridge for a month.
Quarantine may take longer than expected
I bought several of my supplies -for example oil- for 15 or 20 days, but there are already several countries where the quarantine will last for more than a month.
Milk, beer and soft drinks are consumed much more during quarantine

I should have calculated 50% more consumption for being locked up all day. I would exchange two rolls of toilet paper for a good beer !!
A good internet backup
My ISP is behaving quite well, but a good backup connection would not have been bad.
The sweets!

During the year one tries not to have many sweets so as not to get fat, but in quarantine they are necessary. He should have bought at least one candy per quarantine day.
Having more money on checking account
Accustomed to paying for things in cash, I got quite a bit of cash, but I fell a little short in the bank since many things that were paid for in cash -delivery pizza- are now paid online.
Liquid alcohol and bleach
Beyond alcohol gel, toilet paper and kitchen paper, an essential product is alcohol to dilute 70% and clean purchased items.
Popcorn!

Netflix, Amazon Prime and Zulu do not replace cinema without popcorn.
Check all the types of batteries you need
Two AA rechargeable batteries have been ruined and I have no replacement, and it's not as easy as going to the store on the other block. You have to have some quantity. The same with cables and adapters. I am still looking for the cable for my Nintendo 3DS -all games are tested after 20 days locked up-.
Cold remedies

If you have the misfortune to catch a cold in the middle of the quarantine, you don't want to go to the pharmacy. A supply of over-the-counter cold remedies are not superfluous.
This is all I wrote down so far. I hope it helps them and if they have any other tips I hope they share it. Thank you!