1. You don't need to "tame" them. The fish will get to know their surroundings and their owner eventually, just give them time. It is highly important to introduce them to an established tank at the perfect temperature for tropical fish. Make sure that their tank is placed somewhere in your home that has minimal to no traffic. If lots of people walk by your tank daily, it will stress out your fish, causing them to take more time to become "tame" and get used to you.
2. Fruits are too high in citrus acid, it is not recommended that fruit be placed in your tank as it can meddle with the water levels. Soy isn't a great idea as it can pollute your tank. For extra protein, feed your fish blood worms, brine shrimp or meal worms. If you can, get live ones. If not, then ask your local fish store if they have the frozen cubes. If that doesn't work either, the next best thing is freeze-dried. Feed them this once a week for the protein they need. It is also recommended that you fast your fish after doing so, otherwise their digestive systems can get clogged.
As far as vegetables go, most of them are healthy for your fish. Make sure to cook them first in order for the fish to actually be able to eat them. You can't expect tiny guppies to be able to take a bite out of a raw carrot, right? Vegetables will also pollute your water if they sit in it for too long, so it is advised that you only leave the veggies in the tank for one day. Try a few out like celery, de-shelled peas, broccoli, carrots, cucumber and zucchini. It's up to the fish to tell you what they like and what they don't.
3. The same goes with cichlids. Just make sure they're cooked and your fish will give you feedback on what they like and what they do not like.
Good luck!