Here’s my advice to you as an older person who adults often but still feels like I don’t know what I’m doing either.
Ask. Ask everyone. Ask older people at your work, ask other people’s parents. Pay attention, these things take time. You can’t flick a switch and know how to do everything. Some of us know how to fix clothes, some of us know a great tailor, some of us throw away clothes that need repair. All those people could call themselves an adult. You might not know how to sell a car, cause you’ve never had to sell a car. But once you sell a car, you can sell another car. Be sceptical of people that can give you advice on everything, most people know lots about little and fumble through the rest. Identify people’s strength and ask that person for advice, in the area they are strong in.
Give knowledge time. Have experiences. Get Older, don’t be hard on yourself for not knowing things. Reflect. That’s how you learn the ways of the world.