How many minutes a day do you recommend practicing?

Between 10 and 15 minutes a day, every day or almost. This is by far the most effective way: short, frequent sessions build muscle memory much better than a weekly binge. Half an hour on a Sunday does not make up for five days without touching the keyboard.

A couple of recommendations

• Start with the Daily Warm-up: it is short, reviews exactly the keys you struggle with the most, and does not require speed. Plus, it leaves you with multiplied experience for the rest of the day.
• If you feel tired or your accuracy starts to drop, stop. Practicing with messy technique consolidates the mistake, which is the exact opposite of what you want.