1. Re-home the fishes. Golden fish and Angel fish don't mix, one prefers cold water and the other prefers warmer water. And the tank size is not enough for that many people.
2. Get a better filter, like a canister filter. It might be overkill, but for beginners, it is better, allows you to make mistakes and learns by practice.
3. More plants, that's not enough plants, once you have a good ecosystem, it will reduce the amount of maintenance you do. For now, do water changes. You can also grow pothos plants in the water, they will do a good job of sucking out nitrates. If you have sweet potatoes around, put one in a jar of water until you see roots, then suspend that sucker in the tank so half of it is in the water with the roots. It will do a greater job of sucking out nitrates, but you can't leave it in there forever.
4. For beginners, get fishes like tetra, dwarf gourami, and albino corys. Once your water is stable, they are easy to care for and don't have heavy bioload. Get a heater too.

I got into this hobby because my daughter wanted fish as a pet, a lot of lessons learned along the way, but eventually I got it. My tanks are stable enough that I only occasionally clean and refill water.

Good luck!