I am sure that where you live the plant is indoors and does not receive full direct sunlight. The plant knows it needs more light and that is why it is trying to grow into the light. What you must do is give it more artificial light, otherwise, it will grow into a skinny weak trunked tree. And until you have more light try turning the plant a 1/4 turn each day in order to try to keep the trunk straight. But you must give the plant more light. An avocado tree is a tropical plant and Poland is a long way from being in the tropics. Because of this, I am afraid you are just wasting your time and money trying to grow this tree.