Welcome and be welcomed! As all have said, thanks for realizing your error and the courage to want to change your relationship. Regarding food, fruit and veggies, if you wash them off well, pesticides will not be an issue, and both are important to your parrots diet. SLOWLY try to introduce them and wean him off that seed diet - not to scare you but they signifficantly affect your birds lifespan ( In my and many others opinion ). I realize that getting parrot food pellets in Bulgaria may be a challenge, but it will be worth it. I will help you out here, and send samples of a few different types
(I get crazy discount on shipping to Europe). You want to try a few different types and find one he loves and readily eats. My own Salty has pellets ( Roudyboush ) available all day, he gets fruits for breakfast and veggies for dinner. THose sunflower seeds are so not good for him, but the upside is that once he is on a good diet, you can use those for treats and to teach him things.
Regarding training him even now, Sitting quietly next to the cage, with the door open,
offer a few shelled sunflower seeds from your open hand , held near the cage door. The idea is the get him to stand on the opening and eat there. Once he does that comfortably, move the hand further away and introduce your finger on the other hand, so that he has to perch on your finger to get to the treat. ANY improvement or slight movement twords the goal should be accompannied with verbal praise, in a soothing voice ' Good Boy' or the Bulgarian equivalent (LOL). THis whole simple process could take days , weeks or months, but you have to let your parrot set the pace. You might spend 3 weeks just sitting next to the cage door with seeds in your hand, an hour or two each day, before he decides to even investigate OR it could take a day or two before you move to the next step.
But first priority is to get him off the seed diet and eating healthy. Do the veggies first, because they are available immediately. You must read up and find the veggies that are safe and which are not ( like avacadoes are a big no no), then hit the market.
Most parrots LOVe sweet potatoes ( yams), cooked and cooled, and they are good for them. Great place to start. carrots and peppers ( the hotter the better , for my bird).
Offer them separately or chopped fine and mixed together ( known as Chop).
Once you post more on here, you can send me a private message and I can get those pellet samples to you.
post some pics of your little guy and tell us his name !